A wooden box contains six standard and ungaffed pool (snooker/billiard) balls of different colours. The box itself is examinable and seems innocent. With your back turned, you ask one or more spectators to remove a ball of their choice, and put it in a pocket. You will know where each ball is, or who has each ball. You can get this information from the receiver screen, or from a thumper, which can be concealed anywhere on your body. (If you have one of the original Magitronics receivers, this will also work).
The box is powered by a lithium battery and is recharged wirelessly.
The objects need not be pool balls. So long as they fit fairly snugly into the compartments and the lid can close, they can be anything you want.
Versions of this effect were performed as “Colour Psychology” by Al Koran (1957) and “Quantimental” by Ed Mellon (1958). You can see British magician Graham Jolley perform it for a TV audience below.