This has been a long-standing issue. Every time that there's a Sims game, aside from TS3, the same issue crops up. Black hair is the worst.
However, since I learned to recolor, I do give EA some slack on white. It is really, really difficult to get a nice white without the hair or clothing looking blown out. Also, the detail starts to get lost. I'm not sure how to solve that issue. Still, EA could go whiter than they have been. Their "white" is very gray. As well, there is no consistency in the whites (or blacks) across the board.