I don't really think black should be used by any team where it isn't one of their primary colors. The Reds, for example, really need to drop the black highlights and go back to plain old red and white.
As for the multicolor alternate jerseys, I like most of them. The home team always in white and the road team always in gray gets dull after a while. I'd actually like to see more teams use a colored alternate jersey, but a lot of baseball fans and teams are very traditionalist, so I can understand why they don't do it.