Not sure how well this would work, but if the back comes off easily, you can palm the white one, and switch the black one for the white one with "a wave of the hand". Or if you want to gimmick you phone, you could just put a black back on the back of the phone, and put a white one on the top of the phone, and while you are waving your hand, do a Murphy deck flip, and reveal the other colored back. or start with the white "back" which is on the face, do the deck flip to reveal the real back (black), and then palm off the white one and the setup on the face.