Color-blind people are your audience too!
Posted by Helena Jambor, on 27 April 2017
Or, please stop mixing green/red
Color is a key aspect of graphic design, but for many years was not relevant for scientific figures that were largely black and white. Falling prices for color print and electronic publishing changed this dramatically and scientists now frequently produce multi-colored figures. Using color functionally is not always straightforward but few rules exist: do not combine red and green!
Already in 1939 Willard Brinton advised his readers to not use red letters on a green background as they become invisible to color-blind people (and are hideous for the rest of us!). [his great book on data visualization is available for free here]. A century later, when browsing through figures in scientific periodical, this message has not reached everyone.
In charts, it is very straightforward to avoid mixing red and green. If you want to use red, combine it with blue or cyan, if you want to use green, combine it with magenta or orange. That way also color blind people can distinguish the data points. A side note: try starting a chart in black and white, and only add color if absolutely essential.
In laser-microscopy green and red fluorophores are widely used, often in combination. But: Simply because a wavelength of your fluorophore is 488nm this does not mean you have to use green for its display! The camera output doesn’t have color anyway, so you are at liberty to choose a suitable lookup table. Why not be color-blind friendly and choose colors visible to your entire audience. Options that still preserve a little information on the wavelength are green/magenta or cyan/red.
Again, consider if two black and white images instead of a composite color. In fact, the contrast is usually higher in greyscale which benefits the display of structure details and subtle intensity differences.
*Rm62 RNA in Drosophila egg chambers part of my postdoc project, find more subcellular RNAs on the Dresden Ovary Table.
Helpful tools:
- Test color-blind visibility for your images here
- Choose color for categorical, quantitative and diverging data in charts using color-brewer.
Comments suggesting more tools very welcome!
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A very good tip for those not affected by colour blindness is to change your image into grey-scale. If you can see a difference (due to the degree of obscurity of the chosen colour) then a colour blind person will be able to see it, too. For example, if you take the image of the oocyte top left and turn it into grey-scale you will no longer see a difference between the yellow an green regions – and this is what colour-blind people will experience with red/green image.
See also this excellent resource by Kei Ito: http://jfly.iam.u-tokyo.ac.jp/color/
You may also like to have a look at http://www.colourblindawareness.org by @colourblindorg