Super Deck Gamma by Syouma & Tejinaya Magic
Fan the cards, showing normal faces and blue backs. A participant calls out a card from the the fan, and when the selected card is turned over...it has a red back! For a kicker ending, the deck is turned over and shown to be completely blank, now!
Easy to do...the gimmicked cards do all the work for you. Includes one Super Gamma Deck with Bicycle backs and online instructions.