my 1975 Sachs 125 /6D has a yellow, red and green wire. I connected the yellow to the headlight of my Herc GS, using a simply on/off switch. The red wire goes to the tail light directly (it works inductivly, when the headlight is on) and the green one you can use for the stop light switch or a rectifier for charging a battery (for stop light, horn and flashers, if needed).