Headlight Ground-Wire Issues (YAY!)

[panda-supra]

I've got a mysterious problem with my Supra's headlights.
We can't seem to find the ground wire to it. I understand the ground wires are supposed to be marked in white with a black stripe.

More specifically, I have taken my driver side headlight out of its housing and I stare at the headlight plug. The headlihgt plug has three female ports that connect into the bulb, of which I'm guessing one is regular lights hot, bright lights hot, and ground. But which is which? They are all reading hot, no grounds.

The Chilton Manual Diagram isn't being a great help, and we can locate a ground wire for EVERYTHING else in the car BUT the headlights ground.
Can anybody maybe give me more insight into this? Maybe where I can find a better diagram than the Chilton's? Maybe even a physical diagram because we are having trouble locating the headlight ground wire with the logical diagrams out of the Chilton. Thanks bunches.