I personally have a very open mind on the subject. Granted, I've only ever known the Joker as having white skin, but this is a very interesting take on the character.
You see, I'm a huge fan of the Ultimate Marvel Universe. For those that don't know about it (as if), it's a seperate continuity that has virtually every Marvel character reinvented for modern audiences. The characters and the stories are grounded in a much deeper sense of realism, even the god like characters. I'm a huge fan of these books, as it's a new and creative take on my favorite characters while still keeping the spirit the same.
Which brings me to the portrayal of the Joker in The Dark Knight. I'm imagining it in my head....
A cold, sadistic killer with a warped sense of reality and a truly demented sense of humor, easily amused with the death and fear of others. No morals, no feelings that could be considered rational human thought. This psychopath is horribly disfigured at the corners of his mouth, resulting in what looks like a demonic grin. Amused by this, he takes this look a step further by making himself up to resemble a demonic clown, complete with red lipstick that goes up the lacerations and green dye in his hair. Using this face, he proceeds to carry out any actions that come to his diseased imagination. And the more people hurt, and the more people die as a result of his actions, the funnier it is to him, and the harder he laughs.
Wow, you can't tell me that isn't frickin scary. When I think about it like that, it makes a scary amount of sense, and it actually stays true and builds on the character while giving it a fresh spin. I applaude Chris Nolan for being brave enough to try something different while not betraying the character. I think Heath Ledger's Joker is probably going to be the best interpretation of the Joker that we've ever seen. I personally can't wait!