In the RV World SOLID WHITE is GROUND and any other color including BLACK is HOT. My trailer uses alot of White cables with color stripe in it. These are all HOT...
In the AUTOMOTIVE World BLACK is GROUND and RED is HOT. Something they get mixed together in the RV trailers...
The best solution is to measure the two different colors with a MULTIMETER just to be sure...
Just a thought for you on mounting your rear camera - I would make sure it is up high on the trailer pointing down otherwise if using at night the approaching cars will flare out the screen when their headlight hits the camera. Can't see a thing on the screen when this happens...
Something like this GOOGLE IMAGE install is what I would want to do...
Roy Ken