the flywheel what does it say
bosch then a volts /watts
or cev or ducati....
it really just matters on how its wired
top tanks are nearly identical except the tank.
i think it was willD that explained it best when into the wiring of generals.
So there's actually a few different ways they wired those bike, but typically the orange is actually brown and is your ground, black/red is for the brakelight and the white is actually gray and is the taillight.
Yellow is lighting power out of the engine and runs up thru a terminal behind the headlight and goes to the lightswitch on the bars, then that splits to a red wire which goes to the headlight and a gray (you called white) going back to the taillight. sounds like those are all good if your lights are going. The headlight and taillight are both powered off the lighting coil which outputs on the yellow wire from the engine, and the power is dependent on engine RPM since theres no battery and it's normal that they dim at idle. perhaps your bulbs wattage is too high if they're excessively dim.
The brakelight works with an idiotic piece of crap mechanism where it's powered off of the ignition coil. a red/black wire comes out of the engine, and splits, one wire going back to the brake light, and another going through the coasterbrake switch (comes out green) then the green wire goes up to the headlight terminal and to the handbrake switch, and then comes out as a brown wire to ground. the switches are normally closed circuit in the relaxed position, when you pull either switch the circuit opens and the power out of the black/red wire is then grounded through the brakelight - and it lights up.
The retarded thing is if any of the voltages or wattages or anything in the brakelight system is off, then it won't ground right and because it's off the ignition coil, it can kill the bike. WTF.
Anyways you can replace the handbrake switch with another standard open in relaxed style switch from treats and run it parallel off the headlight wire, then just ground the red/black from the engine.
now that you got the full story, here's the short answer:
from bike to new light
Red/black - stoplight - blue
Gray (white) - taillight - yellow
Brown (orange) - ground - green