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When designing for accessibility, one area that often gets overlooked is colour blindness. This might stem from the misconception that there are so few colourblind people that it’s not worth compromising your beautifully customized colour palette. Or perhaps it’s the feeling that people who are colourblind are used to navigating the world of colour, and your designs won’t make a difference in the end.
In reality, the frequency of colour blindness is fairly high. One in 12 Caucasian (8%), one in 20 Asian (5%), and one in 25 African (4%) males are so-called “red-green” colour blind. Globally, around 300 million people are colour blind, making it more common than AB blood type.
The human eye has three types of cone cells, each expressing different types of opsin genes, and each sensitive to red, green and blue respectively (RGB). Colour blindness is when the function of one of these opsins is not optimal.
Colour blindness is not a total loss of colour vision, but rather the loss of clear distinction between certain ranges of colours. The majority of colour blind people have difficulty with reds and greens: protanopia (defective red cone cells) and deuteranopia (defective green cone cells). There is also the more rare tritanopia (defective blue cone cells).
Infographics such as charts, graphs, etc. (and wherever colour is used to distinguish different data) typically pose the biggest difficulty. Especially wherever green and red might appear. But beyond distinguishing between certain colours, other problem areas that characterize colour blindness can include:
Luckily we are not left in the dark. There are many organizations and strategies that can help guide our designs in terms of colourblind accessibility. According to the Principles of Color Universal Design (CUD), here are a few:
The Okabe Ito colour Palette, invented by Masataka Okabe and Kei Ito of Color Universal Design (CUD) in 2002, is a good universal palette whose colours are better distinguished by colour blind people. Although originally created for print, hex values can easily be extrapolated.
IBM has also released a colour blind safe palette that seems to have a more vibrant persuasion, and whose hex values are readily available. And thirdly, Paul Tol’s deep dive into various palettes representing bright, high-contrast, muted, pale, etc, variants of similarly colour blind safe palettes is also quite impressive.
Another suggestion from Okabe and Ito for accessible design is redundant coding, which can include: