I have a fairly new kitten and she is changing color. She was almost all black/brown but now she has a lot of grey. On her underside, underside of her tail, on her legs, tops of her legs, seems like it's slowly going over her whole body.
Don't know what breed of cat she is, was a stray, but is there some breed that does this as they get older? I'll post a picture when I get a new one of her.