The color label may be considered offensive by some people of color - you'd have to ask them, not a random group of strangers on a gaming forum. Why do you have to label your friends by anything other than their name anyway?
The only time I have ever heard "yellow" used in reference to another person, it was in fiction (books, movies) and was generally referring to cowardice, not racial background.

(D'oh, so used to locking threads, I did lock this momentarily. I am leaving it open, assuming you all can have a reasonably discussion about it.)