The ignition switch has four positions, off, on, on with lights and park light. In the lights on position the main switch feeds 12 volts to the brown wire going into the dimmer switch. Blue and red are high and low beam, coming out of the dimmer switch. Tail light receives power via the white wire from the main switch blue wire is brake light. The early Hondas didn't have a dedicated ground wire in the main harness, that makes troubleshooting a bit more difficult at times.