Dying Leather

I've never dyed leather that had been previously dyed. I made a set of motorcycle saddlebags from a side of leather once & dyed them black with a commercially available dye (don't remember what it was, might have been from Tandy). They ended up with a black surface with bits of dark brown showing through. Kind of an antiqued finish. I later read someplace that it's recommended that when you dye something black, you should dye it dark blue first, to get a more even color. That's about all of the personal insight I can give.