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.