This is a diagram that was already on-line in the Tech Links and I assume to be somewhere around late '76 to '78, since it has an ignitor. The wiring and wire colors didn't change much during that time. I did notice a difference between my '76 and my '78 diagrams, in that the wire from the F terminal of the Hazard Switch to the B terminal of the flasher is GO in '78 diagram and GW in '76 diagram. It's not labeled on this pdf diagram.
http://www.ih8mud.com/tech/pdf/fj40_wiring_diagram.pdf
You will find that switches and other devices, OEM and aftermarket, sometimes have different wiring colors than the harness itself, but typically the wires are in the correct locations in the plugs for the function. I just looked at a '76 column that I have out and the 6-pole plug for the turn signal switch has GY, GB, GO, GL, GR, and G wires. There is also a 4-pole plug with RY, RG, and WB wires and a single GW bullet connector. I'll have to do some additional research, since I've noticed that the wiring doesn't necessarily match the wiring diagram, as other noted earlier in this thread.
Yes I saw this diagram somewhere else last night. You see that the turn signal switch is only shown with the G\B Left, G\Y Right and G\L power from flasher. No other wires show at that switch and the other wire colors are not listed. This makes perfect sense, as those should be the only wires needed for left and right turn. I am baffled by my B\L showing 12 V at the switch but drops to 0 if a bulb is attached???? It makes me wonder if it is supposed to do that to trigger the flasher. The flasher gets triggered by the circuit going through the filament to ground, but that being the case where is the pulsed 12 V coming back into the circuit? I know when I pull the Hazard Flasher on the B\L wire at the flasher drops to a low voltage 2-3 volts. The G\Y and G\B wires out of the hazard switch also carry the same low voltage while the G\W direct from the flasher pulses 12 V, so how is 12 getting pulsed to the lights???? I must be missing something fundamental here, but these are the voltage readings I am getting and my meter doesn't lie. Argh!!
Your 76 has the exact same turn signal switch as mine. The red wire harness is for the headlights and I don't have any issues there.
I guess another good question to ask is if I only had the turn signal switch, the flasher, a 12 V battery and a left and right turn signal out side of the truck, how would I wire that to work??