A spectator is handed an oblong block which has a different colour on each side. The spectator places the block in the box, remembering the colour which is on top, and making sure that the magician has not seen the colour. The magician takes the box and, with suitable mystic passes, correctly divines the colour on top. Gamages, Hamleys, International Magic, and no doubt other dealers, sold the trick under the name Telepathic Colours.