What is the color code for 12V wiring?

The 12V color code in most DC systems is red for positive and black for negative. Solar, RV, marine, and battery wiring generally follow it.

Automotive wiring breaks the rule constantly. In vehicles, black is often switched power and grounds may be brown or body metal, and constant-hot wires are frequently red or yellow. Harness diagrams beat color assumptions in a car.

Marine standards use yellow for negative specifically so black cannot be mistaken for an AC hot.

Colors are conventions, not guarantees. A previous owner's repair can put any color anywhere, so confirm polarity with a multimeter before you connect anything that cares about it.

Once polarity is confirmed, size the run with the low voltage wire size calculator; 12V systems lose voltage fast.