It looks like that Optimus headlight has two small amber running lights, high beam and low beam. The first thing to check would be if those headlights are set up as one high beam bulb and one low beam bulb or is it two dual filament bulbs? If it has two dual filament bulbs you will have a problem as Brian posted above. You might have to give up your high beam.
Did you try contacting the ebay seller asking for information?
I'd imagine that black is common ground. If you measure resistance between the black wire and any other wire on the headlight you should get a reading. Measuring between any other two wires would be an open circuit. That will confirm that black is the ground.
Then the easiest way to check after that would be to get some wiring pigtails an connect the black directly to battery ground then connect another wire to green and battery positive (then do the same for yellow, blue and white) and see which light turns on. Then write down the results.
You can probe the bike harness in a similar way.
First confirm a ground.
Then turn the ignition on, only the running lights will have power.
Then start the bike with only low beam on, low beam will have power.
Then turn on high beam, high beam will have power.
Write down your results then match up the wiring.
Ok, I'm still suffereing over this nightmare guys.
Biggest problem is that I cut the old stock headlight out of the harness (And I really dont remember why but it must have been simplicity for the sale).
So...What I'm left with (And this is between the cluster and the plug) 6 open or cut wires (3 on each side) green red grey, and green brown grey.
I'm 99% sure this is where the headlight came from.
I'd be more than happy to text pics is that helps btw (I'm desperate and really don't want to pay a mechanic an hour or more to figure this out).
From the Optimus headlight I'm trying to utilize I've got green white blue black yellow.
On the 2 middle bulbs the green blue and white wires are attached.
From the 2 outer bulbs or turn signals are yellow green and blak and green.
So seeing as Green are in every bulb I'm assuming green is ground???
And I have green coming from both sides in the harness.
I know this is confusing as hell but I'm running out of options.