US AC power circuit wiring color codes The protective ground is green or green with yellow stripe. The neutral is white, the hot (live or active) single phase wires are black , and red in the case of a second active. Three-phase lines are red, black, and blue.

Identifying old wiring is crucial, especially in older buildings or during renovations. Look for the old wiring colours: red for live wires, black for neutral wires, and plain green for earth wires. If these colours are present, it's likely the wiring system predates the 2004 regulations.

Usually the red is marked as + (plus) and the black is marked as – (minus). Notice that in both AC electricity and DC electronics, there is a black wire. But in AC electricity the black is hot (“positive”) whereas in DC electronics black is for negative.