Looking at the orange and purple implemented, they're close to existing colors, so I imagine those would be more for user customization or as alternates for the existing magenta and yellow.
So I just noticed an issue: whenever I try to specify a TM color in Mapview, it comes out instead as black. CSS colors and RGB values work OK, but not TM colors. Oddly enough, your sample "bad-looking combination" link works fine, so I'm not sure what's going on.
Anyone else seeing similar problems? Might be worth force-reloading to make sure tmjsfuncs.js is a fresh copy.
I figured out what happened: TM colors should only be specified once, not separately for clinched and unclinched as other colors are.