Chinese Coin Color Change by Joker Magic

The magician shows the audience a Chinese coin, both sides are black.
He rubs it a little, and both sides of the coin turn red.
Another rub, and both sides of the coin are now blue!
The coin can be examined immediately.

The coin is nickel plated.

• The instructions are supplied through a practical download link. They are in English, but easily understandable by anybody thanks to the clear video.