Give me enough time and...
It is the white wire, as I suspected, which connects to the red wire with blue strip that runs to the lamp itself.
Just to bring you up to date, I have the camera physically installed, but either I have a bad video wire, or I messed up one of the connectors trying to run the wire. If that's the case, I think I'll have to run a wire sans connectors, and solder on the connectors after it's run. There's one spot that is a bear to get the wire with connector through, and that's the rubber conduit that runs from the top of the hatch to the body. You need to be especially careful because the rear washer fluid tube runs through there too. At least if I have to run a new wire I can use the existing wire to draw it through. Here's some pictures...
Here's a little tool I made to get the plastic trim piece off to drill for and mount the camera. This perfectly compresses the rivets and they pop right out. It worked well for those easy to reach, but it was hard to get it to the ones that were more difficult. So I made a longer one, and when I went to use that one, discovered I needed some leverage. Then I had one of those "Doh!" moments, when I realized the trim removal tools I bought on Amazon (which do come in handy) has a perfectly sized hole that must be just for this purpose! If you don't have a tool, a 7/32 inch hole works well.

I made an "error" in the installation, fortunately easy to correct. I don't have any idea what I was thinking, but for some reason I was thinking the license plate lights were the backup lights. Well... They were right there! I realized my error as soon as nothing happened when I went into reverse. I turned on the lights to confirm. Now that I've realized my error, I have to run at least one additional wire through the same circuitous route to the backup light. I'll probably run power and ground.
I broke a few clips... The outer clips on the center rear trim in the cargo area, which are actually part of the trim piece, not separate clips, are pretty lame and broke right off. I also lost one of the clips when putting back the tan seatbelt trim piece in the left rear cargo area. These seem easy to replace.
Here's several pictures from the (not yet completed) installation...





