Using the parameters I've chosen, the following color combinations are possible:
- red/green/purple/cyan + colorless
Colors extreme in both color dimensions must be matched against a colorless shade.
- blue/yellow + aqua/magenta
A color extreme in one dimension must be matched against a color extreme in the other dimension.
Additionally, there will be a contrast of dark or light against middling brightness.
Update: After discussing some of these schemes with ctwardy, I've added a further rule: for the red/green/purple/cyan+colorless schemes, the body of the text must be the colorless one.
Appendix: Rarely used color terms
A bluish cyan and a light blue:
We tend not to distinguish between cyan and light blue, which is a pity because light blue is an awesome color.
Magenta, another rarely used color term:
Don't confuse dark magenta (aka Tyrian purple) with dark red or purple.
Both Tyrian purple and what we now call purple have been associated with richness and royalty, but Tyrian purple would be contrasted with gold, whereas our modern purple would be contrasted with white.