I like this idea... multicolored hair is always awesome. And no, MLP people, rainbow actually existed before your ponies so it's not a reference to that.
hmm you do have good point....we could do half and half, 1/3, 1/4, until it is filled like the rainbow colors.
Pretty much fits this part of the thread. Clearly multiple types of colored hair is a NPC/Boss/Race. I'm just joking about. But I do like the idea.
It doesn't even have to be that extravagent, some multi-colored hair styles are very good looking and not too complicated.