In one hand, the magician has a white brass chip with a white middle, in the other hand a black one. Both hands are closed, and when opened, the white chip is now black, the black one now white. This is repeated with a playing card between the chips, and still the chips change color. When the spectator is convinced that the chips are only black on one side and white on the other, the chips are shown again, but now one is green and yellow, the other red and blue. Startling!
The same effect as Black and White Surprise, or Chameleon Coins, for those who know this trick by those names.