The wiring to the sockets is probably tin plated copper mot aluninum. Traffic signal cable is manufactured to IMSA standards and for a 3 section head you would a cable with a RED for red ball YELLOW for yellow ball GREEN for green ball. WHITE for common if there is an green arrow for left turn it would be on a BLACK.At this time i cannot remember what color a yellow left turn arrow is fed with. remember that in the wiring going io the signal head that green is power to the green ball (indication) NOT GROUND.
