Red: Red wires are used as phase wires and they carry electrical current. The various colored wires that you can see when you look behind a switch or an outlet are not an accident, but rather a safety feature that is built in. If you need more detailed information, continue reading this article. They also reduce the risk. So, it is equally important to be aware about the old wiring color code. Under this scheme, the line conductor was red, the neutral conductor was black, and the earth conductor was green with a yellow strip for single-phase systems. Ground wires protect an electric system from power surges during events like lightning strikes that would cause voltage spikes on any other line in the system.