Snow Blind by Bob Solari - Trick

Effect:
Four-of-a-kind cards are shown and turned face down. The back of each cars is shown to have a Blue back. The performer asks the spectator "Which one of the cards had a Red back?" The spectator responds with "None."

...The performer say's "are you sure, I think you may be snow blind." The performer turns the four cards face down, showing them each to ahve White backs!