You'll be delighted by the clever gimmicks that are used to accomplish this effect. The attractive props are easy to see, but they can fit in your pocket, making this a versatile that can be performed up close or on stage. A simple frame is shown, containing three square plaques, each a different color: Red, Yellow, and Green.
The performer removes the plaques, mixes them, and returns them to the frame in a new arrangement. He keeps the backs toward the audience, so the order of the colors is kept secret.
Three large plastic clips are brought out, also red, yellow, and green.
Members of the audience are asked to decide where the clips should be placed along the edge of the frame.
Their choices are free and uninfluenced -- the arrangement of the clips is completely fair.
Nevertheless, amazingly, when the frame is turned around it is seen that the positions of the clips and the plaques match up exactly!