Our color (and level!) handling – data structures and interface – has a few problems:
1) the interfaces are pretty bad/unintuitive. We're reusing some controls I found to show a color gradient, and pick colors. There's lots of ways these could be improved for usability.
2) There are new features we'd like to add: remembering sets of colors, etc.
3) Discrete color support (in elements) has been bolted on quite badly to the current stuff, and could do with improvements.
4) The data structures aren't great: they're using a few open source classes we found, and store everything in the XYZ color space. Also, they don't have good support for discrete colors.