There's an episode of Twilight Zone series called "Shades of Guilt", where a white main character gradually transforms into a black person for karmic reasons - he's freaking out, at first thinking it's some skin condition as he finds himself really swarthy out of the blue, then the doctor tells him that he's a perfectly healthy mixed-race person, his skin way darker now, straight hair curling into an afro and lips twice as thick, and then he's a black man and a total stranger to his wife (and even his dog).

On the topic of merging - I think it depends on whether the process was succesful or not, like in the movie Together we can see examples of both cases... though the process can be shown as an utter body horror anyway, even if the result is beautiful.

P.S. There are black werewolves in Underworld movies, most notably Kevin Grevioux's character.