Pick a better color scheme for multiple distributions plots

[berekuk]

Previously: #1266

[mlochbaum]

For pure line plots, I've found ColorBrewer's Set1 to work quite well; I use it here. It's a little small with only 8 colors. For area plots I think you'd want to lighten them some but it should still work.

I used a generative method for another project, described here. This is a graph with a bunch of samples selected. Main code for this is here. It's fairly compact.

[Hazelfire]

I closed #1266 because after conversation with Ozzie, I decided to split up the colour schemes of multi-distribution plots with normal plots, which will become a refactor in #1243. We should get this soon when I fix this refactor <3

[Hazelfire]

Completed in #1388