I just went out and looked at the wires on my 74 20' and my 75 22' Argosy's and the circuit colors on both (3 circuits each coach) are yellow, pink, and violet (purple). The are all about #14 wire, and are fused at 15 amps each.
White is usually negative (-) and red or sometimes black are (+) battery wires, and are larger, usually #10 wire.
Hope that helps a little.
You can take a 12 volt
source such as a battery charger and connect the negative to some good ground metal in the rig, then put the + on each of the wires one at a time, and go and investigate what turns on (lights, fans, water pump etc.) as another way to test things. Just be sure your battery charger is an old style one, which has hot leads all the time. Many new ones will not turn on until they see the proper polarity and voltage of a battery.