use plot colors that compensate for colorblindness

[markvanderloo]

The default colors may not be easily distinguishable for people with colorblindness. We should somehow make it easier to choose colors that compensate for that, or perhaps change the defaults.

[mbannert]

file free to assign me when this needs validation ;)

[edwindj]

Good one:

• we should provide an option that a user provides their own colors.
• since R 3.6 there is a set of really good color palletes in grDevices: https://developer.r-project.org/Blog/public/2019/04/01/hcl-based-color-palettes-in-grdevices
• tricky part: many qualitative palettes (categorical) are notoriously difficult for color blindness, because qualitative palette do not differ in lightness/saturation.
• therefor in data visualisation often a blue vs red is used instead of green vs red, because these colors are more distinct for most types of color blindness

[edwindj]

(so in base R there is hcl.colors and hcl.pals

[markvanderloo]

I used this online colorblindness simulator to simulate colorblindness and copy-pasted the simulations (completely irreproducibly) into some slides. The current colors do not seem too bad in the simulation but I don't feel in the position to judge.

validate-colorblindness.pdf

[modche]

Thanks, nice effort here to have better colours. Have you looked into the Color palette proposed by Okabe and Ito (https://github.com/clauswilke/colorblindr/blob/master/R/palettes.R), implemented in the colorblindr package from @clauswilke. I guess this categorical palette is quite good. However, if you tune the plot output also a width parameter (to have smaller columns for each test with whitespace between) and larger labels would be nice.

--Michael

[edwindj]

Thanks! The Okabe and Ito palette is also available in grDevices:

palette.colors(palette = "Okabe-Ito")

##         black        orange       skyblue   bluishgreen        yellow 
##     "#000000"     "#E69F00"     "#56B4E9"     "#009E73"     "#F0E442" 
##          blue    vermillion reddishpurple          gray 
##     "#0072B2"     "#D55E00"     "#CC79A7"     "#999999"

[markvanderloo]

How about a black & white option? Matt pointed out on Slack that the current colors are hard to distinguish in low contrast circumstances. R now has the option to shade surfaces in different patterns. I will experiment a little with that.