4 wire color changing LED Xmas lights

[JoeG]

This is seriously not computer related, but I still need some input.

I have a pre-lit Christmas tree that has coloring changing mini LED lights on it. When the lights are switched to White only (via a foot switch), all of the lights works. But when I change it to multicolor, about 10 lights don't light up. I think I found which socket has gone bad (for some reason). The socket has two wires going into one side, and one wire going into the other side. There's a four wire that doesn't connect to the socket. I would like to test the wires to see which one is possibly not providing power to the socket in color mode. I might have to splice the socket out as well.

My question is, how is the socket likely wired with regards to power and ground?

I've attached a diagram.

Any help is greatly appreciated!

Joe