This is a very easy yet extremely baffling mystery. The secret is amazing, and makes for a very mystifying close up effect. The trick consists of the precision made brass tube and five different coloured (anodized) metal rods, in a bag.
The performer displays a solid metal tube, and several different coloured metal rods. A spectator places any of the rods in the tube, closes it, and hands it over to the performer. The other rods are concealed by the spectator. The performer feels the vibrations from the tube, and reveals the colour of the rod in the tube. The apparatus can be examined, and the effect repeated as often as you like.