The magician gives a blue backed deck to a spectator explaining it contains a prediction. Then he says he has another deck, but it's very special; it's an invisible deck.
A spectator chooses a suit from the invisible deck and then he selects any value with absolute freedom, for example the 5 of Clubs. The magician takes the blue backed deck and when he spreads the cards, everyone can see there's only one card face up: it's the 5 of Clubs. Then he turns the 5 of Clubs face down, showing it's the only card with a red back.
But that's not all; the magician spreads all the deck showing all card have blank face.