Add colorblind mode / adjust colors

[UJehle]

We should check if the color scales that we currently use (e.g. in the heatmap) are also visible for color-blind people. We could either think about adjusting the colors accordingly or implement a setting that switches to "colorblind" mode.

See: https://www.tableau.com/about/blog/2016/4/examining-data-viz-rules-dont-use-red-green-together-53463 https://davidmathlogic.com/colorblind/#%23D81B60-%231E88E5-%23FFC107-%233A9E2E