Modern Times by Henry Evans

The magician displays one red and one blue deck of cards, each still in their boxes. One of the decks is chosen by a spectator and with a little shake, the performer makes the box visibly disappear, leaving the loose deck of cards in his hands! The missing box is then removed from his pocket. Next, after showing the faces and backs of the cards clearly, the magician tosses the deck onto the table and the backs visibly change color! Upon opening the other box, the specator's chosen deck is found inside.

Henry's opening effect from his 2000 FISM World Champion in Card Magic award-winning act.