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What the Color of an Electrical Wire Means for You

If you live in the United States and your home was built after the 1940s (or your outdated wiring has since been updated), you can expect the electrical wires behind your walls to follow certain color standards. Specific colors identify each wire’s function in a circuit. Learning what these color codes are before attempting any type of do-it-yourself (DIY) electrical system repairs is critical.

Just remember, all electrical wires could carry a current at some point, so treat each color with equal caution. If you have any hesitations at all, it’s best to leave electrical work to a qualified professional.

Black Electrical Wires

This color of wire is used to transfer power to switches and outlets in all types of circuits. Black wires are also often used as switch legs in circuits, which is the connection linking a switch to the electrical load. Consider all black wires to be live at all times.

Red Electrical Wires

In 220-volt circuits, red wires are the secondary live wires. Like black wires, they can be used in some types of switch legs. They are also used to connect hardwired smoke detectors to the home’s power system. It’s possible to link two red wires together or a red wire to a black wire.

Blue and Yellow Electrical Wires

While wires in these colors carry power, they are not used in typical outlet wiring. Instead, blue and yellow wires are used as the live wires pulled through a conduit. For example, you might see yellow wires as switch legs to ceiling fans, structural lights and outlets paired with light switches. Then, blue wires are most often used as travelers for three- or four-way switches.

White and Gray Electrical Wires

If you find wires in either of these colors, you’ve located the neutral wires. White is most commonly used, but gray wires serve the same function. The purpose of a neutral wire is to connect to the neutral bus bar, a conductive piece of metal within an electrical panel that attracts the electric current for distribution throughout the house. White and gray electrical wires can only be connected to one another. While they’re called “neutral” wires, they may still carry a current, especially if the load is unbalanced, so handle them cautiously.

Green Electrical Wires

The purpose of green wires is to ground an electrical circuit. They connect to the grounding terminal in an outlet box and run to the ground bus bar in an electrical panel. In this way, green wires act as a failsafe, giving electricity a place to escape into the ground if a live wire within the circuit touches metal or something else conductive. Green wires can only connect to other green wires. Remember, if there’s a fault somewhere in your circuit, green wires could be live, so treat them with caution.

With this wire color code guide, you have a better idea of what wires accomplish which tasks. You may feel comfortable completing simple electrical upgrades yourself, but the service professionals at Mr. Electric® can handle the job for you.