diff --git a/blockly_uncompressed.js b/blockly_uncompressed.js
index c3b5961e8..ab92a378d 100644
--- a/blockly_uncompressed.js
+++ b/blockly_uncompressed.js
@@ -89,12 +89,14 @@ goog.addDependency("../../core/options.js", ['Blockly.Options'], ['Blockly.utils
 goog.addDependency("../../core/procedures.js", ['Blockly.Procedures'], ['Blockly.Blocks', 'Blockly.constants', 'Blockly.Events', 'Blockly.Events.BlockChange', 'Blockly.Field', 'Blockly.Msg', 'Blockly.Names', 'Blockly.utils.xml', 'Blockly.Workspace', 'Blockly.Xml']);
 goog.addDependency("../../core/rendered_connection.js", ['Blockly.RenderedConnection'], ['Blockly.Connection', 'Blockly.Events', 'Blockly.utils', 'Blockly.utils.Coordinate', 'Blockly.utils.dom', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/common/block_rendering.js", ['Blockly.blockRendering'], ['Blockly.utils.object']);
+goog.addDependency("../../core/renderers/common/colourer.js", ['Blockly.blockRendering.Colourer', 'Blockly.blockRendering.IColourer'], ['Blockly.blockRendering.IPathObject']);
 goog.addDependency("../../core/renderers/common/constants.js", ['Blockly.blockRendering.ConstantProvider'], ['Blockly.utils.svgPaths']);
 goog.addDependency("../../core/renderers/common/debugger.js", ['Blockly.blockRendering.Debug'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.Types']);
 goog.addDependency("../../core/renderers/common/drawer.js", ['Blockly.blockRendering.Drawer'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.Types', 'Blockly.utils.svgPaths']);
 goog.addDependency("../../core/renderers/common/info.js", ['Blockly.blockRendering.RenderInfo'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.Hat', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.InRowSpacer', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.RoundCorner', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.SquareCorner', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.Types']);
 goog.addDependency("../../core/renderers/common/path_object.js", ['Blockly.blockRendering.IPathObject', 'Blockly.blockRendering.PathObject'], ['Blockly.utils.dom']);
-goog.addDependency("../../core/renderers/common/renderer.js", ['Blockly.blockRendering.Renderer'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.blockRendering.Drawer', 'Blockly.blockRendering.IPathObject', 'Blockly.blockRendering.PathObject', 'Blockly.blockRendering.RenderInfo', 'Blockly.CursorSvg']);
+goog.addDependency("../../core/renderers/common/renderer.js", ['Blockly.blockRendering.Renderer'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.blockRendering.Drawer', 'Blockly.blockRendering.IPathObject', 'Blockly.blockRendering.PathObject', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.IColourer', 'Blockly.CursorSvg']);
+goog.addDependency("../../core/renderers/geras/colourer.js", ['Blockly.geras.Colourer'], ['Blockly.geras.PathObject']);
 goog.addDependency("../../core/renderers/geras/constants.js", ['Blockly.geras.ConstantProvider'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/geras/drawer.js", ['Blockly.geras.Drawer'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.blockRendering.Drawer', 'Blockly.geras.Highlighter', 'Blockly.geras.PathObject', 'Blockly.geras.RenderInfo', 'Blockly.utils.object', 'Blockly.utils.svgPaths']);
 goog.addDependency("../../core/renderers/geras/highlight_constants.js", ['Blockly.geras.HighlightConstantProvider'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.utils.svgPaths']);
@@ -102,7 +104,7 @@ goog.addDependency("../../core/renderers/geras/highlighter.js", ['Blockly.geras.
 goog.addDependency("../../core/renderers/geras/info.js", ['Blockly.geras', 'Blockly.geras.RenderInfo'], ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.Types', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.geras.InlineInput', 'Blockly.geras.StatementInput', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/geras/measurables/inputs.js", ['Blockly.geras.InlineInput', 'Blockly.geras.StatementInput'], ['Blockly.utils.object']);
 goog.addDependency("../../core/renderers/geras/path_object.js", ['Blockly.geras.PathObject'], ['Blockly.blockRendering.IPathObject', 'Blockly.utils.dom']);
-goog.addDependency("../../core/renderers/geras/renderer.js", ['Blockly.geras.Renderer'], ['Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.geras.ConstantProvider', 'Blockly.geras.Drawer', 'Blockly.geras.HighlightConstantProvider', 'Blockly.geras.PathObject', 'Blockly.geras.RenderInfo', 'Blockly.utils.object']);
+goog.addDependency("../../core/renderers/geras/renderer.js", ['Blockly.geras.Renderer'], ['Blockly.blockRendering', 'Blockly.blockRendering.Renderer', 'Blockly.geras.ConstantProvider', 'Blockly.geras.Colourer', 'Blockly.geras.Drawer', 'Blockly.geras.HighlightConstantProvider', 'Blockly.geras.PathObject', 'Blockly.geras.RenderInfo', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/measurables/base.js", ['Blockly.blockRendering.Measurable'], ['Blockly.blockRendering.Types']);
 goog.addDependency("../../core/renderers/measurables/connections.js", ['Blockly.blockRendering.Connection', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.blockRendering.PreviousConnection'], ['Blockly.blockRendering.Measurable', 'Blockly.blockRendering.Types', 'Blockly.utils.object']);
 goog.addDependency("../../core/renderers/measurables/inputs.js", ['Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.InputConnection', 'Blockly.blockRendering.StatementInput'], ['Blockly.blockRendering.Connection', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.Types', 'Blockly.utils.object']);
diff --git a/core/block.js b/core/block.js
index c61bc1280..2b0ce8d34 100644
--- a/core/block.js
+++ b/core/block.js
@@ -905,63 +905,10 @@ Blockly.Block.prototype.setTooltip = function(newTip) {
  * @return {string} #RRGGBB string.
  */
 Blockly.Block.prototype.getColour = function() {
+  // TODO: Can we remove this?
   return this.colour_;
 };
 
-/**
- * Get the secondary colour of a block.
- * @return {?string} #RRGGBB string.
- */
-Blockly.Block.prototype.getColourSecondary = function() {
-  return this.colourSecondary_;
-};
-
-/**
- * Get the tertiary colour of a block.
- * @return {?string} #RRGGBB string.
- */
-Blockly.Block.prototype.getColourTertiary = function() {
-  return this.colourTertiary_;
-};
-
-/**
- * Get the shadow colour of a block.
- * @return {?string} #RRGGBB string.
- */
-Blockly.Block.prototype.getColourShadow = function() {
-  var colourSecondary = this.getColourSecondary();
-  if (colourSecondary) {
-    return colourSecondary;
-  }
-  return Blockly.utils.colour.blend('#fff', this.getColour(), 0.6);
-};
-
-/**
- * Get the border colour(s) of a block.
- * @return {{colourDark, colourLight, colourBorder}} An object containing
- *     colour values for the border(s) of the block. If the block is using a
- *     style the colourBorder will be defined and equal to the tertiary colour
- *     of the style (#RRGGBB string). Otherwise the colourDark and colourLight
- *     attributes will be defined (#RRGGBB strings).
- * @package
- */
-Blockly.Block.prototype.getColourBorder = function() {
-  var colourTertiary = this.getColourTertiary();
-  if (colourTertiary) {
-    return {
-      colourBorder: colourTertiary,
-      colourLight: null,
-      colourDark: null
-    };
-  }
-  var colour = this.getColour();
-  return {
-    colourBorder: null,
-    colourLight: Blockly.utils.colour.blend('#fff', colour, 0.3),
-    colourDark: Blockly.utils.colour.blend('#000', colour, 0.2)
-  };
-};
-
 /**
  * Get the name of the block style.
  * @return {?string} Name of the block style.
@@ -984,48 +931,20 @@ Blockly.Block.prototype.getHue = function() {
  *     or a message reference string pointing to one of those two values.
  */
 Blockly.Block.prototype.setColour = function(colour) {
-  var dereferenced = (typeof colour == 'string') ?
-      Blockly.utils.replaceMessageReferences(colour) : colour;
-
-  var hue = Number(dereferenced);
-  if (!isNaN(hue) && 0 <= hue && hue <= 360) {
-    this.hue_ = hue;
-    this.colour_ = Blockly.hueToHex(hue);
-  } else {
-    var hex = Blockly.utils.colour.parse(dereferenced);
-    if (hex) {
-      this.colour_ = hex;
-      // Only store hue if colour is set as a hue.
-      this.hue_ = null;
-    } else {
-      var errorMsg = 'Invalid colour: "' + dereferenced + '"';
-      if (colour != dereferenced) {
-        errorMsg += ' (from "' + colour + '")';
-      }
-      throw Error(errorMsg);
-    }
-  }
+  // Set colour just stores these as properties on the block, but never uses
+  // them again.
+  // TODO: see if we can just get rid of these properties on the block.
+  var parsed = Blockly.blockRendering.Colourer.parseColour(colour);
+  this.hue_ = parsed.hue;
+  this.colour_ = parsed.colour;
 };
 
 /**
  * Set the style and colour values of a block.
  * @param {string} blockStyleName Name of the block style
- * @throws {Error} if the block style does not exist.
  */
 Blockly.Block.prototype.setStyle = function(blockStyleName) {
-  var theme = this.workspace.getTheme();
-  var blockStyle = theme.getBlockStyle(blockStyleName);
   this.styleName_ = blockStyleName;
-
-  if (blockStyle) {
-    this.colourSecondary_ = blockStyle['colourSecondary'];
-    this.colourTertiary_ = blockStyle['colourTertiary'];
-    this.hat = blockStyle.hat;
-    // Set colour will trigger an updateColour() on a block_svg
-    this.setColour(blockStyle['colourPrimary']);
-  } else {
-    throw Error('Invalid style name: ' + blockStyleName);
-  }
 };
 
 /**
diff --git a/core/block_svg.js b/core/block_svg.js
index b404e27fb..8af8b9e66 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -71,6 +71,14 @@ Blockly.BlockSvg = function(workspace, prototypeName, opt_id) {
   this.pathObject =
       workspace.getRenderer().makePathObject(this.svgGroup_);
 
+  /**
+   * [colourer description]
+   * @type {[type]}
+   * @package
+   */
+  this.colourer =
+      workspace.getRenderer().makeColourer(this, this.pathObject);
+
   // The next three paths are set only for backwards compatibility reasons.
   /**
    * The dark path of the block.
@@ -267,7 +275,7 @@ Blockly.BlockSvg.prototype.initSvg = function() {
   for (var i = 0; i < icons.length; i++) {
     icons[i].createIcon();
   }
-  this.updateColour();
+  this.applyColour();
   this.updateMovable();
   var svg = this.getSvgRoot();
   if (!this.workspace.options.readOnly && !this.eventsInit_ && svg) {
@@ -939,7 +947,7 @@ Blockly.BlockSvg.prototype.setEditable = function(editable) {
  */
 Blockly.BlockSvg.prototype.setShadow = function(shadow) {
   Blockly.BlockSvg.superClass_.setShadow.call(this, shadow);
-  this.updateColour();
+  this.applyColour();
 };
 
 /**
@@ -1033,69 +1041,30 @@ Blockly.BlockSvg.prototype.dispose = function(healStack, animate) {
 
 /**
  * Change the colour of a block.
+ * @package
  */
-Blockly.BlockSvg.prototype.updateColour = function() {
+Blockly.BlockSvg.prototype.applyColour = function() {
   if (!this.isEnabled()) {
     // Disabled blocks don't have colour.
     return;
   }
 
-  if (this.isShadow()) {
-    this.setShadowColour_();
-  } else {
-    this.setBorderColour_();
-    this.svgPath_.setAttribute('fill', this.getColour());
-  }
+  this.colourer.applyColour(this.isShadow());
 
   var icons = this.getIcons();
   for (var i = 0; i < icons.length; i++) {
-    icons[i].updateColour();
+    // TODO: Decide whether to make icon and field applyColour take in a
+    // colourer object.
+    icons[i].applyColour();
   }
 
   for (var x = 0, input; input = this.inputList[x]; x++) {
     for (var y = 0, field; field = input.fieldRow[y]; y++) {
-      field.updateColour();
+      field.applyColour();
     }
   }
 };
 
-/**
- * Sets the colour of the border.
- * Removes the light and dark paths if a border colour is defined.
- * @private
- */
-Blockly.BlockSvg.prototype.setBorderColour_ = function() {
-  var borderColours = this.getColourBorder();
-  if (borderColours.colourBorder) {
-    this.svgPathLight_.style.display = 'none';
-    this.svgPathDark_.style.display = 'none';
-
-    this.svgPath_.setAttribute('stroke', borderColours.colourBorder);
-  } else {
-    this.svgPathLight_.style.display = '';
-    this.svgPathDark_.style.display = '';
-    this.svgPath_.setAttribute('stroke', 'none');
-
-    this.svgPathLight_.setAttribute('stroke', borderColours.colourLight);
-    this.svgPathDark_.setAttribute('fill', borderColours.colourDark);
-  }
-};
-
-/**
- * Sets the colour of shadow blocks.
- * @return {?string} The background colour of the block.
- * @private
- */
-Blockly.BlockSvg.prototype.setShadowColour_ = function() {
-  var shadowColour = this.getColourShadow() || '';
-
-  this.svgPathLight_.style.display = 'none';
-  this.svgPathDark_.setAttribute('fill', shadowColour);
-  this.svgPath_.setAttribute('stroke', 'none');
-  this.svgPath_.setAttribute('fill', shadowColour);
-  return shadowColour;
-};
-
 /**
  * Enable or disable a block.
  */
@@ -1111,7 +1080,7 @@ Blockly.BlockSvg.prototype.updateDisabled = function() {
     var removed = Blockly.utils.dom.removeClass(
         /** @type {!Element} */ (this.svgGroup_), 'blocklyDisabled');
     if (removed) {
-      this.updateColour();
+      this.applyColour();
     }
   }
   var children = this.getChildren(false);
@@ -1340,15 +1309,40 @@ Blockly.BlockSvg.prototype.setDeleteStyle = function(enable) {
 // Overrides of functions on Blockly.Block that take into account whether the
 // block has been rendered.
 
+/**
+ * Get the colour of a block.
+ * @return {string} #RRGGBB string.
+ */
+Blockly.BlockSvg.prototype.getColour = function() {
+  return this.colourer.getColour();
+};
+
 /**
  * Change the colour of a block.
  * @param {number|string} colour HSV hue value, or #RRGGBB string.
  */
 Blockly.BlockSvg.prototype.setColour = function(colour) {
   Blockly.BlockSvg.superClass_.setColour.call(this, colour);
+  this.colourer.setColour(colour);
+  this.applyColour();
+};
 
-  if (this.rendered) {
-    this.updateColour();
+/**
+ * Set the style and colour values of a block.
+ * @param {string} blockStyleName Name of the block style
+ * @throws {Error} if the block style does not exist.
+ */
+Blockly.BlockSvg.prototype.setStyle = function(blockStyleName) {
+  var theme = this.workspace.getTheme();
+  var blockStyle = theme.getBlockStyle(blockStyleName);
+  this.styleName_ = blockStyleName;
+
+  if (blockStyle) {
+    this.hat = blockStyle.hat;
+    this.colourer.setFromStyle(blockStyle);
+    this.applyColour();
+  } else {
+    throw Error('Invalid style name: ' + blockStyleName);
   }
 };
 
diff --git a/core/comment.js b/core/comment.js
index 31f3942bc..680b6ca95 100644
--- a/core/comment.js
+++ b/core/comment.js
@@ -247,7 +247,7 @@ Blockly.Comment.prototype.createEditableBubble_ = function() {
   // Expose this comment's block's ID on its top-level SVG group.
   this.bubble_.setSvgId(this.block_.id);
   this.bubble_.registerResizeEvent(this.onBubbleResize_.bind(this));
-  this.updateColour();
+  this.applyColour();
 };
 
 /**
diff --git a/core/field.js b/core/field.js
index ee7cc7d17..0b13b7bdb 100644
--- a/core/field.js
+++ b/core/field.js
@@ -603,10 +603,10 @@ Blockly.Field.prototype.getSvgRoot = function() {
 
 /**
  * Updates the field to match the colour/style of the block. Should only be
- * called by BlockSvg.updateColour().
+ * called by BlockSvg.applyColour().
  * @package
  */
-Blockly.Field.prototype.updateColour = function() {
+Blockly.Field.prototype.applyColour = function() {
   // Non-abstract sub-classes may wish to implement this. See FieldDropdown.
 };
 
diff --git a/core/field_angle.js b/core/field_angle.js
index eb26c4597..1025824e6 100644
--- a/core/field_angle.js
+++ b/core/field_angle.js
@@ -269,9 +269,9 @@ Blockly.FieldAngle.prototype.showEditor_ = function() {
   var editor = this.dropdownCreate_();
   Blockly.DropDownDiv.getContentDiv().appendChild(editor);
 
-  var border = this.sourceBlock_.getColourBorder();
-  border = border.colourBorder || border.colourLight;
-  Blockly.DropDownDiv.setColour(this.sourceBlock_.getColour(), border);
+  var colourer = this.sourceBlock_.colourer;
+  Blockly.DropDownDiv.setColour(colourer.getColour(),
+      colourer.getBorderColour());
 
   Blockly.DropDownDiv.showPositionedByField(
       this, this.dropdownDispose_.bind(this));
diff --git a/core/field_date.js b/core/field_date.js
index ebbfbc562..9ed4f68bd 100644
--- a/core/field_date.js
+++ b/core/field_date.js
@@ -129,9 +129,9 @@ Blockly.FieldDate.prototype.render_ = function() {
  * Updates the field's colours to match those of the block.
  * @package
  */
-Blockly.FieldDate.prototype.updateColour = function() {
-  this.todayColour_ = this.sourceBlock_.getColour();
-  this.selectedColour_ = this.sourceBlock_.getColourShadow();
+Blockly.FieldDate.prototype.applyColour = function() {
+  this.todayColour_ = this.sourceBlock_.colourer.getColour();
+  this.selectedColour_ = this.sourceBlock_.colourer.getShadowColour();
   this.updateEditor_();
 };
 
diff --git a/core/field_dropdown.js b/core/field_dropdown.js
index 3a67f6be4..9c59069f3 100644
--- a/core/field_dropdown.js
+++ b/core/field_dropdown.js
@@ -468,13 +468,13 @@ Blockly.FieldDropdown.prototype.doValueUpdate_ = function(newValue) {
  * Updates the dropdown arrow to match the colour/style of the block.
  * @package
  */
-Blockly.FieldDropdown.prototype.updateColour = function() {
+Blockly.FieldDropdown.prototype.applyColour = function() {
   // Update arrow's colour.
   if (this.sourceBlock_ && this.arrow_) {
     if (this.sourceBlock_.isShadow()) {
-      this.arrow_.style.fill = this.sourceBlock_.getColourShadow();
+      this.arrow_.style.fill = this.sourceBlock_.colourer.getColourShadow();
     } else {
-      this.arrow_.style.fill = this.sourceBlock_.getColour();
+      this.arrow_.style.fill = this.sourceBlock_.colourer.getColour();
     }
   }
 };
diff --git a/core/icon.js b/core/icon.js
index bf2c9043a..5b3a28a23 100644
--- a/core/icon.js
+++ b/core/icon.js
@@ -139,9 +139,9 @@ Blockly.Icon.prototype.iconClick_ = function(e) {
 /**
  * Change the colour of the associated bubble to match its block.
  */
-Blockly.Icon.prototype.updateColour = function() {
+Blockly.Icon.prototype.applyColour = function() {
   if (this.isVisible()) {
-    this.bubble_.setColour(this.block_.getColour());
+    this.bubble_.setColour(this.block_.colourer.getColour());
   }
 };
 
diff --git a/core/mutator.js b/core/mutator.js
index 46ed7070d..061420dbc 100644
--- a/core/mutator.js
+++ b/core/mutator.js
@@ -322,7 +322,7 @@ Blockly.Mutator.prototype.setVisible = function(visible) {
     this.resizeBubble_();
     // When the mutator's workspace changes, update the source block.
     this.workspace_.addChangeListener(this.workspaceChanged_.bind(this));
-    this.updateColour();
+    this.applyColour();
   } else {
     // Dispose of the bubble.
     this.svgDialog_ = null;
diff --git a/core/renderers/common/colourer.js b/core/renderers/common/colourer.js
new file mode 100644
index 000000000..563c0fec3
--- /dev/null
+++ b/core/renderers/common/colourer.js
@@ -0,0 +1,131 @@
+/**
+ * @license
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview
+ * @author fenichel@google.com (Rachel Fenichel)
+ */
+'use strict';
+
+goog.provide('Blockly.blockRendering.Colourer');
+goog.provide('Blockly.blockRendering.IColourer');
+
+goog.require('Blockly.blockRendering.IPathObject');
+
+/**
+ * An interface for a block's colourer object.
+ * @param {!SVGElement} _root The root SVG element.
+ * @interface
+ */
+Blockly.blockRendering.IColourer = function(block, pathObject) {};
+
+/**
+ * )
+ * @param {[type]} block [description]
+ * @param {[type]} pathObject [description]
+ * @implements {Blockly.blockRendering.IColourer}
+ * @constructor
+ */
+Blockly.blockRendering.Colourer = function(block, pathObject) {
+  this.block = block;
+  /**
+   * The renderer's path object.
+   * @type {Blockly.blockRendering.IPathObject}
+   * @package
+   */
+  this.pathObject = /** {Blockly.BlockRender.PathObject} */ (pathObject);
+
+  this.svgPath = this.pathObject.svgPath;
+
+  this.hue_;
+  this.colour_;
+  this.colourSecondary_;
+  this.colourTertiary_;
+};
+
+Blockly.blockRendering.Colourer.prototype.applyColours = function(isShadow) {
+  if (isShadow) {
+    this.svgPath.setAttribute('stroke', 'none');
+    this.svgPath.setAttribute('fill', this.colourSecondary_);
+  } else {
+    this.svgPath.setAttribute('stroke', this.colourTertiary_);
+    this.svgPath.setAttribute('fill', this.colour_);
+  }
+};
+
+/**
+ * Change the colour of a block.
+ * @param {number|string} colour HSV hue value (0 to 360), #RRGGBB string,
+ *     or a message reference string pointing to one of those two values.
+ */
+Blockly.blockRendering.Colourer.prototype.setColour = function(colour) {
+  console.log('todo: set colour');
+  // this.colour_ = colour;
+  // this.colourSecondary_ = Blockly.utils.colour.blend('#fff', this.colour, 0.6);
+  // this.colourTertiary_ = Blockly.utils.colour.blend('#fff', this.colour, 0.3);
+};
+
+Blockly.blockRendering.Colourer.prototype.setFromStyle = function(blockStyle) {
+  this.parseColour(blockStyle['colourPrimary']);
+  this.colourSecondary_ = blockStyle['colourSecondary'] ||
+      Blockly.utils.colour.blend('#fff', this.colour_, 0.6);
+  this.colourTertiary_ = blockStyle['colourTertiary'] ||
+      Blockly.utils.colour.blend('#fff', this.colour_, 0.3);
+};
+
+Blockly.blockRendering.Colourer.prototype.getBorderColour = function() {
+  return this.colourTertiary_;
+};
+
+Blockly.blockRendering.Colourer.prototype.getShadowColour = function() {
+  return this.colourSecondary_;
+};
+
+/**
+ * Change the colour of a block.
+ * @param {number|string} colour HSV hue value (0 to 360), #RRGGBB string,
+ *     or a message reference string pointing to one of those two values.
+ * @return {{hue: ?number, colour: string}} An object containing the colour as
+ *     a #RRGGBB string, and the hue if the input was an HSV hue value.
+ */
+Blockly.blockRendering.Colourer.parseColour = function(colour) {
+  var dereferenced = (typeof colour == 'string') ?
+      Blockly.utils.replaceMessageReferences(colour) : colour;
+
+  var hue = Number(dereferenced);
+  if (!isNaN(hue) && 0 <= hue && hue <= 360) {
+    return {
+      hue: hue,
+      colour: Blockly.hueToHex(hue)
+    };
+  } else {
+    var hex = Blockly.utils.colour.parse(dereferenced);
+    if (hex) {
+      // Only store hue if colour is set as a hue.
+      return {
+        hue: null,
+        colour: hex
+      };
+    } else {
+      var errorMsg = 'Invalid colour: "' + dereferenced + '"';
+      if (colour != dereferenced) {
+        errorMsg += ' (from "' + colour + '")';
+      }
+      throw Error(errorMsg);
+    }
+  }
+};
diff --git a/core/renderers/common/renderer.js b/core/renderers/common/renderer.js
index 49a83943a..c9d19902e 100644
--- a/core/renderers/common/renderer.js
+++ b/core/renderers/common/renderer.js
@@ -28,6 +28,8 @@ goog.require('Blockly.blockRendering.Drawer');
 goog.require('Blockly.blockRendering.IPathObject');
 goog.require('Blockly.blockRendering.PathObject');
 goog.require('Blockly.blockRendering.RenderInfo');
+goog.require('Blockly.blockRendering.IColourer');
+goog.require('Blockly.blockRendering.Colourer');
 goog.require('Blockly.CursorSvg');
 
 goog.requireType('Blockly.blockRendering.Debug');
@@ -125,6 +127,18 @@ Blockly.blockRendering.Renderer.prototype.makePathObject = function(root) {
   return new Blockly.blockRendering.PathObject(root);
 };
 
+/**
+ * Create a new instance of a renderer path object.
+ * @param {!Blockly.BlockSvg} block The root SVG element.
+ * @param {!Blockly.blockRendering.IPathObject} pathObject [description]
+ * @return {!Blockly.blockRendering.IColourer} The renderer path object.
+ * @package
+ */
+Blockly.blockRendering.Renderer.prototype.makeColourer = function(block,
+    pathObject) {
+  return new Blockly.blockRendering.Colourer(block, pathObject);
+};
+
 /**
  * Get the current renderer's constant provider.  We assume that when this is
  * called, the renderer has already been initialized.
diff --git a/core/renderers/geras/colourer.js b/core/renderers/geras/colourer.js
new file mode 100644
index 000000000..eb8548cd7
--- /dev/null
+++ b/core/renderers/geras/colourer.js
@@ -0,0 +1,119 @@
+/**
+ * @license
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview
+ * @author fenichel@google.com (Rachel Fenichel)
+ */
+'use strict';
+
+goog.provide('Blockly.geras.Colourer');
+
+goog.require('Blockly.geras.PathObject');
+
+
+/**
+ * )
+ * @param {[type]} block [description]
+ * @param {[type]} pathObject [description]
+ * @implements {Blockly.blockRendering.IColourer}
+ * @constructor
+ */
+Blockly.geras.Colourer = function(block, pathObject) {
+  /**
+   * The renderer's path object.
+   * @type {Blockly.geras.PathObject}
+   * @package
+   */
+  this.pathObject = /** {Blockly.geras.PathObject} */ (pathObject);
+
+  this.svgPath = this.pathObject.svgPath;
+  this.svgPathLight = this.pathObject.svgPathLight;
+  this.svgPathDark = this.pathObject.svgPathDark;
+  this.svgPath.setAttribute('stroke', 'none');
+  this.svgPathLight.style.display = '';
+  this.svgPathDark.setAttribute('display', '');
+
+  this.colour_;
+  this.colourTertiary_;
+  this.colourDark_;
+  this.colourSecondary_;
+  this.styleName_;
+};
+
+Blockly.geras.Colourer.prototype.applyColour = function(isShadow) {
+  if (isShadow) {
+    this.svgPathLight.style.display = 'none';
+    this.svgPathDark.setAttribute('fill', this.colourSecondary_);
+    this.svgPath.setAttribute('stroke', 'none');
+    this.svgPath.setAttribute('fill', this.colourSecondary_);
+  } else {
+    this.svgPathLight.style.display = '';
+    this.svgPathDark.style.display = '';
+    this.svgPath.setAttribute('stroke', 'none');
+    this.svgPathLight.setAttribute('stroke', this.colourTertiary_);
+    this.svgPathDark.setAttribute('fill', this.colourDark_);
+    this.svgPath.setAttribute('fill', this.colour_);
+  }
+};
+
+/**
+ * Get the colour of a block.
+ * @return {string} #RRGGBB string.
+ */
+Blockly.geras.Colourer.prototype.getColour = function() {
+  return this.colour_;
+};
+
+Blockly.geras.Colourer.prototype.getShadowColour = function() {
+  return this.colourSecondary_;
+};
+
+Blockly.geras.Colourer.prototype.getBorderColour = function() {
+  return this.colourTertiary_;
+};
+
+Blockly.geras.Colourer.prototype.setColourFromTriplet = function(primary,
+    secondary, tertiary) {
+  this.colour_ = primary;
+  this.colourSecondary_ = secondary ||
+      Blockly.utils.colour.blend('#fff', primary, 0.6);
+  this.colourTertiary_ = tertiary ||
+      Blockly.utils.colour.blend('#fff', primary, 0.3);
+  this.colourDark_ = tertiary ||
+      Blockly.utils.colour.blend('#000', primary, 0.2);
+};
+
+/**
+ * Change the colour of a block.
+ * @param {number|string} colour HSV hue value (0 to 360), #RRGGBB string,
+ *     or a message reference string pointing to one of those two values.
+ */
+Blockly.geras.Colourer.prototype.setColour = function(colour) {
+  var primary = Blockly.blockRendering.Colourer.parseColour(colour).colour;
+  this.setColourFromTriplet(primary, null, null);
+};
+
+Blockly.geras.Colourer.prototype.setFromStyle = function(blockStyle) {
+  var primary =
+      Blockly.blockRendering.Colourer.parseColour(blockStyle['colourPrimary'])
+          .colour;
+  this.setColourFromTriplet(primary,
+      blockStyle['colourSecondary'],
+      blockStyle['colourTertiary']);
+};
+
diff --git a/core/renderers/geras/renderer.js b/core/renderers/geras/renderer.js
index fcd5e516d..f5745e361 100644
--- a/core/renderers/geras/renderer.js
+++ b/core/renderers/geras/renderer.js
@@ -26,6 +26,7 @@ goog.provide('Blockly.geras.Renderer');
 goog.require('Blockly.blockRendering');
 goog.require('Blockly.blockRendering.Renderer');
 goog.require('Blockly.geras.ConstantProvider');
+goog.require('Blockly.geras.Colourer');
 goog.require('Blockly.geras.Drawer');
 goog.require('Blockly.geras.HighlightConstantProvider');
 goog.require('Blockly.geras.PathObject');
@@ -106,6 +107,18 @@ Blockly.geras.Renderer.prototype.makePathObject = function(root) {
   return new Blockly.geras.PathObject(root);
 };
 
+/**
+ * Create a new instance of a renderer path object.
+ * @param {!Blockly.BlockSvg} block The root SVG element.
+ * @param {!Blockly.geras.IPathObject} pathObject [description]
+ * @return {!Blockly.geras.Colourer} The renderer path object.
+ * @package
+ */
+Blockly.geras.Renderer.prototype.makeColourer = function(block,
+    pathObject) {
+  return new Blockly.geras.Colourer(block, pathObject);
+};
+
 /**
  * Create a new instance of the renderer's highlight constant provider.
  * @return {!Blockly.geras.HighlightConstantProvider} The highlight constant
diff --git a/core/warning.js b/core/warning.js
index fe9f8c4f7..fde0bd50c 100644
--- a/core/warning.js
+++ b/core/warning.js
@@ -149,7 +149,7 @@ Blockly.Warning.prototype.createBubble = function() {
       textElement.setAttribute('x', maxWidth + Blockly.Bubble.BORDER_WIDTH);
     }
   }
-  this.updateColour();
+  this.applyColour();
 };
 
 /**