Do Bels look dirty at all before they shed? Does their white get less white or something?
Well there is the Dirty Bel which is Mojave x Mojave. gives them a greish head, with slight yellows. Not all are always 100% white they could have pinkish or lil marks, I think the best combo to make cleanest bell is Russo x Russo, or Lesser x Mojave/Butter.