The Nutters and other similar dancers black their faces with soot as an informal, token disguise. There hasn't ever, so far as I know, been any suggestion that they are "blacking up" in the way the Minstrel Shows did it; except from outsiders who are bringing their own cultural baggage and preconceptions to a situation where they don't belong (BBC TV producers in the last example I heard about). Quite a lot of ceremonial dance in parts of Africa involves whitening the face with ashes, and there is no racist implication there, either; though to the disguise element is sometimes added a religious aspect also (white being associated with the spirit world, if I remember correctly).