Sunday, June 26, 2016

Red-green color schemes in visualization are tricky

I'm following the results of the Spanish presidential elections and have just seen this map of participation. It uses a diverging color scheme to show the difference in comparison to the previous election.

Red and green color palettes are tricky. Color blind people with deuteranopia have a hard time with them. I ran the map through this application and here are the results:

I've made this mistake myself in the past (see here). Please, always check your color schemes. There are multiple places (1, 2, 3, 4...) where you can read about safe palettes for visualization. Use them.


  1. There's probably a self-selecting bias among graphics designers and artists in general. Colorblind people probably avoid fields they struggle with, so designers likely rarely encounter colleagues with colorblindness.

    It's important that any designer knows how common colorblindness is:
    Men with Red-Green colorblindness - 1 in 10
    Women with Red-Green colorblindness - 1 in 250 (thanks to a backup X chromosome)
    People with Blue-Yellow colorblindness - 1 in 10,000 (very rare)

  2. Try this for an approximation of the different types of colour vision impairment.
    It's not perfect but it gives an idea of some of the difficulties faced. Speaking as someone with protanomaly - red weakness.