About one in 12 men and one in 200 women in the world is color blind. No need to explain that it will also affect scientists. For color blind scientists many graphs and figures are very hard to interpret correctly. Especially because many authors appear to prefer the use of green and red to distinguish points and lines in graphs. Not only authors, but also editors of journals and reviewers should pay attention to this problem. And not only for publications but also for grant applications. What if one of your grant reviewers is color blind, will he or she still be able to understand your research?

Problematic images for the color blind

Here is an excellent article by two color blind scientists, Masataka Okabe and Kei Ito, explaining color vision, color blindness, and how scientific graphs and figures are often difficult to interpret for color blind scientists.

Figure by Okabe and Ito showing the colors that protanope, deuteranope, and tritanope colour blind people see in fluorescence images and microarray

In addition to discussing the problems that choices of colors in graphs can cause,  Okabe and Ito also provide solutions, for instance by showing how to change the colors of images taken with fluorescence microscopes using imaging manipulation software. They also have recommendations for color drawings and presentations, in summary these come down to:

• Select colors that are easy to distinguish for color blind people
• Do not convey information with color only, also use differences in shape ( for instance: continuous vs dotted lines)
• Add a link from each label to the corresponding line, instead of in a legend to the side
• For box plots use differences in patterning of the box in addition to the color
• During a presentation do not refer to an object by the name of its color but rather point it out or refer to it by shape or position.
• Do not use red laser pointers during a presentation, color blind people can often not see what it points at.

various colors and how they are perceived by people with various types of color blindness

Tools to ‘color blind-proof’ your publications

There are various tools that can help you color blind-proof the images for your publications. One of them is Color Oracle which is a free tool that lets you apply a filter to your screen that will show you how a color blind person will see your images.  If you use Adobe Photoshop or Illustrator you can simulate color blindness by creating a proof (go to View > Proof Setup > Color Blindness).

For general advice on how to choose colors for scientific graphs, not only to improve comprehension by color blinds, but also to improve understanding of your graphs in general, you may want to check out this article by Doug McNeall.

Note: I noticed that the link to the excellent article by Okabe and Ito is not always working, you can however find the colour palet on Mike Mol´s page. For your convenience I have copied the color schemes from Mike Mol’s page below.

Codes for colors that can be easily distinguished