If I remember correctly, dark elves are purple in some states because there are laws against painting up your face black. Then again, I heard that when I was like... 16. So it was probably a lie.
Actually, in Pennsylvania there is or was a "Minstrel Law" where you are not allowed to walk around in public impersonating a "Black" person... the vaudeville definition with a blacked-out face. I have no idea if this law is even in effect anymore, but I wash off my make up before leaving the site just in case.