Stereo wiring on 2002 Silverado - Sorry for the delay Machster69 -- believe it or not, after several months since my initial post, I only recently got the aftermarket radio ...

Sorry for the delay Machster69 -- believe it or not, after several months since my initial post, I only recently got the aftermarket radio working (I wasn't driving the truck a whole lot, so it wasn't essential.) Turns out there was a loose connnection elsewhere (behind the instrument cluster) that was preventing the radio from working. But it's all operating fine now.

As for the color coding of the radio wiring on the 2002 Silverado 1500, Damion's posted reply was essentially correct. My truck doesn't have a factory amp, so my harness has only one orange wire (which is the constant 12V+). And it has no power antenna either.

After connecting the constant 12V, the switched 12V (ignition), the ground wire, the illumination wire, and the eight speaker wires (4 sets), there were three unused wires in the factory harness that I taped off: one light gray (dimmer wire), one dark green (probably the vehicle speed signal (VSS) for the speed-sensitive volume on the factory radio), and one dark-green-white-stripe (unknown, but possibly the 'E&C' wire according to some diagrams I've seen).

FYI, I found that using a flashlight battery to identify speaker wires by "popping" each speaker was helpful. The battery makes a mild static noise in the speaker when connected to the corresponding wires. This made it easy to match the speaker wires in the vehicle harness to the aftermarket radio harness.