The foss4g "The Toolmakers Guide" video is an excellent discussion of what we wrestle with in GeoTools.
As a follow up to color-brewer Mike Bostock introduces CUBE HELIX offering a progression of intensity, which also rotates through hue (forming a spiral through the RGB color space). You can rotate the spiral a bit to make visually distinct maps (and avoid all maps looking like an "angry watermelon").
Here is a link I found:
It would be nice add this palette generation options to gt-palette.