Electrical Wiring: What’s color got to do with it?

electrical wiresYou pull a light switch to install a dimmer or open a junction box to run a new line. Suddenly you’re confronted with a maze of wires with different color insulation. The colors distinguish the current each wire carries. Noteworthy, absolutely. Don’t ignore them or you could have a serious problem.

Decades ago, the National Electrical Code (NEC) specified color coding for wiring in the U.S. Over the years, the U.S. and Canada have cooperated to harmonize their country color codes to the point that today they’re nearly identical. The exception to that rule being that certain hot wires are coded in high-voltage applications. Steps are being taken to standardize color coding internationally, but significant variations still exist. If you are working with foreign-made fixtures or appliances, be sure you know which wires carry what type of current before connecting them.

The explanations below apply only to U.S. and Canadian wiring--standard 110/120-volt household wiring.

Black Wire

This is the “hot wire,” the one that carries the current. It provides power to outlets and switches and is often used as switch legs. Most fixtures and switches use brass or copper-colored screws to identify the hot connection points. Never use a black wire as a neutral or ground wire because it can lead to dangerous accidents. NOTE: some installations may use a red wire as the hot wire, and red wires can also carry current in switch legs and hard-wired smoke detectors.

White or Gray Wire

This is the “neutral” or return wire on grounded 110/120-volt circuits. It carries current back to the power source to complete a circuit and is only active when the circuit is active. It should only be connected to the neutral terminal in an outlet or junction box. Neutral terminals are usually designated by silver-colored screws. You can also identify the neutral side of a three-prong outlet by looking at the slots. The neutral side has the larger rectangular opening. The smaller one is on the hot side. White wires are sometimes used in switch legs, but should always be marked to indicate they are not neutral.

Green, Green and Yellow Striped or Bare Wire

A green or bare copper wire is the ground wire that gives a safe path for electricity to flow in case of a short in the circuit. It gives an internal path so that the current doesn’t reach the fixture or appliance and shock you or start a fire. Appliances and switches have grounding screws that the wire is connected to and junction boxes are grounded to themselves. Those screws are usually marked with a green coating. Some ground wires may also have yellow stripes. The thing to remember is “green = ground.”

Higher-voltage wiring

208/220/240-volt circuits require a second hot wire to deliver the higher voltage. The second hot wire is often red, but can also be blue or yellow or even white. A white wire should always be marked to show it’s not being used as a neutral to avoid mistakes. Higher voltages in the 400-volt range are common in industrial settings, but are rarely, if ever, found in household wiring and should only be worked on by licensed electricians.


• Green, Green with Yellow Stripes, and Bare Wire: Ground wires only
• Black: Hot wire only
• White or Gray: Neutral. Sometimes a second hot or in switch legs, but should be marked as such
• Red: Hot wire, switch legs, smoke detectors
• Blue: Second hot wire, or hot in 3- and 4-way switches
• Yellow: Usually in switch legs with outlets, fans, or lights, but can also be a second hot wire

When in Doubt, Call a Pro

Always follow good practices when working with electricity. Improper wiring can result in poor service, fire danger, and electrocution. Never undertake an electrical project if you are unsure how to do it correctly and safely. Licensed electrical professionals have the tools, knowledge and experience to do the job right. Trying to save money by doing an electrical job without the proper skills can cost you both money and safety in the long run.

The pros at Allstar Electrical Services are ready to help you with any electrical needs or concerns, large or small. We’ve been serving the Front Range for nearly 15 years and are top-rated by the BBB and Angie’s List.

Visit our website, allstarelectrical.com, and see the many ways we can serve your electrical needs.

Residential Safety Blanket

Residential Safety Blanket

Sign up today for Allstar Electrical Services residential Safety Blanket program. You'll get a free electrical assessment as well as being able to count on same-day repair service.

Service Areas

Service Areas

All Service Areas »

Server Room Wiring

Featured Service

Our professional, uniformed team is licensed, bonded and insured. We'll respond same-day for an time for an appointment.