Most of the popups I have worked will have a white ground wire and a black positive wire. But where does the Red wires come into play. Campers I have seen are wired like homes. Its a home on wheels ..... Right. Both the AC and DC circuits use the same colors ..... usually Black for power and White for ground. But your Tow Vehicle is not a home on wheels and are usually wired differently ........ Black is used a lot as a ground wire and red as a power wire. The equipment that is added to a camper can and usually does use the automobile wire code. The power tongue jack, water pump etc could use this automotive code. So if you find a red wire connected to your camper search what it is connected to and you should find it has a black wire instead of white for a ground wire and connect accordingly. I try to mark battery wires and even paint the black odd ground wires white and the red black so I can correctly connect them the next time I service/change a battery.