Yes but those figures/characters have their own place as legitimate characters on screen in the G1 cartoon.
Other recolours have had letters designated to them with their MP number when they re-released moulds as characters from other transformers continuities. Eg: MP11S, MP12G.
Although some might argue that MP13B should have had it's own number given that Soundblaster was a legit character in (Japanese) G1 also. Meh.