I've had two black cats and one black dog. I've heard it's harder to get people to take black animals, and I'm not sure why. I do know the lady we bought our old dog from encouraged us to get her tattooed (this was before microchipping) because she said black animals were more likely to get stolen (and allegedly used in rituals), which I'm a bit skeptical about. One thing I can attest to about black pets is they are slightly more likely to be hit by cars (which is what happened to black cat #1).
Oh, and black cat #1 haunts my parents' house. Take that for "superstitious" if you like.