Missing colors in statistics committee chart

One-sentence description

We ran out of colors for all our committees

Current behaviour / Reproducing the bug

Check the middle graph in https://thalia.nu/members/statistics/

Expected behaviour

We can just reuse other colors in my opinion. Or decide on which colors to use based on the total number of colors required (if 1 → magenta, is 2 → magenta and black, 3 or more → generate a list of shades ranging from full black to magenta to white).