Not sure if this was posted somewhere in the previously 80+ pages of the thread, but Michael Caine's given an interview where he seems to confirm that this Joker is, in fact a guy with "normal" skin and hair who puts on makeup and hair dye:
  • When you see the make-up -- he looks like he's mentally gone. He puts the make-up on to disguise himself and then goes and never takes it off again, or washes, so gradually it looks like leprosy. I'm a great fan of Christopher Nolan. I thought 'Batman Begins' was the best Batman I'd ever seen. And I think this one will be better than that.”