The magician makes a bet indicating that he always knows the position of a selected card even after the deck has been mixed.
The spectator chooses a card from the red deck and mix, when the magician stops, he says that the card is for example in position 22.
But the card has disappeared from the red deck and the red card is in position 22 in the blue deck that has been in sight since the start under a glass containing the bet money.