Brake light wiring WTF

[DieselDetroit]

so I'm pretty sure my truck was an ex Walt Disney vehicle and Mickey Mouse was the primary mechanic.

I ripped out at least 3-4 yards of bogus and unused and looped wiring. I've got everything back to stock and here's my question:

The main tail light harness. I always thought it was 4 wires. Yellow/green/brown/black or whatever it is. Anywasys, I'm poking around and I see a 5th wire. Well my gues is someone went in the loom and tapped or spliced for power - nope. I went back halfway down the frame and opened the loom, still 5 wires, it's like a peachy mustard. Color. It's a 5th wire and I don't know where it goes?

Can you guys help? I followed it to where it came from and it was another power for a brake light for a historic canopy. I have it taped off right now.

Thanks

 

[someotherguy]

Yellow - left turn/brake.
Dark green - right turn/brake
Light green - reverse
Brown - tails/tag light
Black - ground

Richard

 

[Eskimomann209]

There's a white one sometimes
For the reverse indicator on electric brakes No?

 

[Bob L]

Look for evidence of a cap in the past. Someone may have run a brake light wire from the third brake light to the rear for a brake light in the cap.