Working with a tangle of live wires and electricity is much safer when adhering to industry color codes. Wire colors are often the quickest way an electrician or qualified worker can identify the electrical wire they are working with. It’s critical for anyone who will be working with wires on a daily basis to have a full understanding of wire color codes.
The US National Electrical Code (NFPA 70), the standard for safe installation of electrical wiring and equipment, mandates neutral wires to be grey or white and provides an industry consensus for other wire colors:
- Black is used for negative wires in a direct current (DC) power system and for phase 1 wiring in an alternating current (AC) power system with 120, 208, or 240 volts.
- Red wire colors are used to represent a positive wire for DC power and for phase 2 wires in AC power (120/208/240 volts).
- Grey and white is used for DC power ground wires and are required to be used for neutral wiring in AC power systems; white is used for systems carrying 120, 208, or 240 volts and higher-voltage connections (277/480 volts) should have grey neutral wires.
- Green is only used in AC power systems for ground wires. Ground wiring can either be a solid green or green with a yellow stripe in the middle.
- Blue wires are almost exclusively used to represent phase 3 wiring systems in lower-voltage systems (120/208/240 volts)
- Brown wires are used in AC power systems carrying 277 or 480 volts to represent phase 1 wiring.
- Yellow is also used in higher-power AC systems (277/480 volts) for phase 3 wiring.
- Orange is used sparingly for wires carrying 120, 208 or 240 wires to indicate a high-leg connection (one phase with a higher voltage than the others) and is used for phase 2 wiring in higher-voltage wires.
These are industry standards used in the United States and wire color coding is often different from country to country. For instance, most of Europe follows the codes established by the International Electrotechnical Commission, Canada follows the Canadian Electric Code, and the wire colors in the United Kingdom are regulated by the Institution of Engineering and Technology.