---
description: How colours affect accessibility.
title: Colour and accessibility
image: images/blockly_banner.png
---

# Colour and accessibility

Blockly uses colour as a strong hint about the role of each block, and to group
blocks together. For the included blocks, this affordance is secondary to the
text on the block, and so not a critical attribute. However, when choosing a
block colour palette, colour blindness should be a consideration.

Blockly provides [several
themes](/guides/configure/appearance/themes#built-in) in an effort
to accommodate some types of colour vision deficiency. [This
page](http://mkweb.bcgsc.ca/colorblind/palettes.mhtml#projecthome) includes
example 8, 12, 15, and 24 colour palettes that attempt to maximize distinction
across the most common forms of colour blindness. Note that this wouldn't map to
8, 12, 15, or 24 block categories in Blockly, because some shades should be
reserved for shadow blocks and fields.
