I won't implement such a feature (too specific, and useless added bloat for 99% of the users, me included).
However, I implemented
Lua scripting precisely to cover such needs, and I will add in next release a Lua callback for chat
text coloring (not the names, sorry: those are made into SLURL links and are colored as such). Basically, all you will need is scripting something akin to this (here to color Friend's chat text in pink: another kind of feature I won't implement otherwise):
Of course, you will have to maintain a Lua table (with id/color couples) to achieve what you want, but it's very easy to script.