Sorry, I have a '76 550K. It's been pretty bastardized though, so I have no idea what's stock and what's not.
When I got it, the green/red wire came out of the main harness, then into a green terminal that went back into the main harness. The same green terminal also had grounds going to each headlight bolt. None of these wires had anything to do with the aftermarket turn signals that had their own "custom" wiring.
Interesting that black/red isn't a Honda color. That black/red wire to the aftermarket start witch looks like it comes out of the main harness, and looks just like the other 35 year old wires.
Cal, I will run another ground to the frame. Good idea.
Thanks.
TF