Here’s a circuit for making your own flashing color party lights for Halloween (also called a color organ), you can pick up all the parts at RadioShack, assuming your local RadioShack is one of the ones that still has electronic parts… – “The following pictoral diagram illustrates how to wire the elements of a “direct connect” color organ, which uses 12 volt bulbs. Critical parts are listed as Radio-Shack part numbers. The power transformer will be the most expensive item (max. $10). Since this color organ uses half wave rectified voltage, a 25 volt transformer is used. A choice of power transformer is given since the “1366” has a capacity of 1.0 amp (at 12 volts), while the “1512” has a capacity of about 4.0 amps. This device is connected directly to any 8-ohm source of sound, such as the speaker output jack of any sound system.” [via] – Link.