The tail light harness that comes from the front of the truck meets the rear harness at a connector. The harness has 4 wires. Dark Green, Light Green, Brown(possibly black), and Yellow. Does anyone know what wire does what function (tail, stop, left, right)? I want to wire in trailer light socket off the truck and Its cold to probe the harness on the ground with a helper or brick. I mean, I can do it but if someone just already knows that would be helpful. I tried my 1980 service manual but I could not find the color meanings unless Im just not looking in the right spot.