Making figures comprehensible for colour-blind readers

There has been some discussion in Nature‘s Correspondence section about the difficulty experienced by colour blind readers in interpreting colour figures.

Chris Miall of the University of Birmingham, UK, started the topic in his letter pointing out that a significant number of readers cannot distinguish red from green. He cited issue 7120 of Nature, which, he says, contains six figures whose only two colours are red and green.

John Runions, of Oxford Brookes University, UK, then pointed out that magenta and yellow, a combination apparently encouraged by some journals, are not a good combination either. From his letter: "Magenta and yellow in overlay produce ’almost white’ — virtually indistinguishable from the yellow in tiny images. Red and green, the standard colour pair, produce yellow when overlaid, and this is very easy to interpret. I suggest that journals continue to publish these images in red/green, but that they make alternatively coloured images available online as supplementary information for readers who have impaired colour vision."

Last week, Joseph Ross of the Fred Hutchinson Cancer Research Center in Seattle drew attention to an excellent website. From his letter:

“As a red-green colour–blind (deuteranope) scientist and graphic designer, I have long campaigned for figures to be accessible to an entire audience. I do so, in part, by leading seminars training my colleagues to create accessible figures.

One of the key resources I employ in this crusade is a ”">website by Masataka Okabe and Kei Ito: ‘How to make figures and presentations that are friendly to color-blind people’.

I strongly urge all authors to visit this site, which both describes the need for creating accessible images (including simulations of colour-blindness for those who are curious) and, more importantly, provides instructions for making figures comprehensible to everyone. This includes instructions on how to pseudo-colour images containing red and green fluorescent signals — one of the most hated types of graphic among people with colour-blindness. Authors will find it is surprisingly easy to accommodate the colour-blind when creating figures.

Anyone who needs to be convinced that making scientific images more accessible is a worthwhile task should consider that colour-blindness is common, affecting 5–10% of males. If your next grant or manuscript submission contains colour figures, what if some of your reviewers are colour-blind? Will they be able to appreciate your figures? Considering the competition for funding and for publication, can you afford the possibility of frustrating your audience? The solution is at hand."


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