Follow Old Bisquits instructions and don't guess at it. You can do it by disconnecting all of the wires and grounding the TT with the truck by using the hitch or a jumper cable. Then turn on your running lights and start touching one wire at a time while holding a fuse in between and see what lights up. Then write it down and don't try to remember it for even five minutes because you can lose confidence in that time. Electrons are color blind and don't care what color the insulation is. My FIL was color blind but could wire his truck lights easily. Identify and mark with masking tape too.