Color-blind people are your audience too!

This article is also on TheNode http://thenode.biologists.com/color-blind-audiences/photo/

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.

Red/Green line chart

Color-blind friendly

Alternative with no color and direct data labels

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.

Overlapping data is problematic

color-blind friendly

Alternative without color and with direct data labels

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.

Red/Green Confocal image

Color-blind friendly

*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.

Comment suggesting more tools very welcome!