I don't think any of the organisations mentioned are in a position to "ban" anything. Just to ask their members not to do this. Unless there is actually a law prohibiting it I suggest that we talk about suggestions rather than bans.

I used to black up for a pace-egg play but became uncomfortable with it so I stopped. I don't have anything against other people doing it if they want. I can see nothing wrong with using other colours. Except for the Brittania 'nutters. I cannot see them in any colour but black!

Out of interest, when looking at old B&W photos of Morris teams I wondered what colours they really used :-) But that is just my lateral brain.