Using a very loose definition of "discriminated against..." Let's just say that having blue hair severely limits one's job opportunities. Recently, I've been able to get around it by wearing a (hot, itchy, uncomfortable) wig to work.
I don't think that sort of appearance-based discrimination is on the same level as discrimination based on race, gender, sexual preference, religion, etc. After all, I chose to dye my hair blue, and I have the option of covering it up or dyeing it brown again. Still, it does affect my life, and it's pretty systematic--it's difficult to find a job where blue hair isn't, at the very least, a strike against you in the interview. Hopefully that will change as people become more open-minded.