Hmm. I don't want to take the dash out to take some pics at the moment.
Although, if I recall, the colored wires corresponded exactly to the colors on most USB cables (black red green white). I just matched them up - not 100% sure on this, but it was pretty much a no-brainer.
If I'm not correct - since I said this, I'm sure that there are units out there with different colored wires - then just get your multimeter out and test continuity from the contacts on the board to the contact pads on the factory USB cable. Then you can map them yourself and be sure that everything is perfect.