I believe that is right, green is low, yellow is high. Mine was actually brighter on low then it was on high before I took the stock headlight off.
^You are indeed correct.^ The green lead sends power to the low beam light, and the yellow lead delivers juice to the high beam. Now, let me see if I can't clear up some of these light-related questions...
First of all, a headlight that works ONLY on hi OR low beam is subject to an open or shorted circuit somewhere. I'd first test for the presence of DC power in the suspected bad lead. For example, if your high beam isn't working, probe the yellow lead with a volt meter to see if a minimum of 9 volts is present there with the switch in the 'HI' position and the engine idling. Similarly, if the low beam isn't working, do the same test on the green lead.
Got juice? Clean the contacts in the headlight socket, and if that doesn't work, try a new bulb. One filament is likely burned-out or shorted in the bulb, or corrosion in the light socket is preventing a good connection from being made.
No juice present? Oops! Then there isn't any power making it to the suspect circuit to begin with. Time to take apart the headlight switch on the handlebars and clean out the affected contacts. You may discover that something is broken or bent in there. This would result in an open circuit, and therefore no power to the light. If damaged contacts are determined to be the problem, you'll need to R&R the headlight switch. If you can't find anything wrong with the headlight switch, contacts, or bulb filaments, do a continuity test across the two contacts on the suspect circuit. Test the high-beam switch to be sure that the switch contacts are closing, or do the same with the low-beam switch, as needed. A switch that won't close stops the power right then and there.
Whew! Sorry to be so long-winded
, but perhaps that rant will wind up helping somebody...