Electrical Wire Color Codes

What it is

Conductor color identifies what the conductor does in the circuit. In the US, the NEC strictly controls only a few colors: the grounded conductor (neutral), the equipment grounding conductor, and the high leg of a 4-wire delta. The colors for ungrounded (hot) conductors are mostly convention. Where a building has more than one voltage system, NEC 210.5(C) and 215.12(C) require the identification scheme to be posted.

How to identify

• Grounded conductor (neutral): white or gray insulation, or three continuous white or gray stripes on insulation that is not green (NEC 200.6). Larger sizes can be field-marked at terminations.
• Equipment grounding conductor: bare, green, or green with one or more yellow stripes (NEC 250.119). Larger sizes can be field-marked.
• High leg (4-wire delta): marked orange or otherwise effectively identified (NEC 110.15).
• Ungrounded (hot) conductors: any color other than white, gray or green. Follow local practice and the posted identification scheme.

Color table

Machine control wiring (NFPA 79, typical): black for ungrounded AC and DC power at supply voltage; red for ungrounded AC control; blue for ungrounded DC control; orange (yellow also recognized) for circuits that stay live when the main disconnect is off; white or gray for grounded AC; white with blue stripe for grounded DC; green or green with yellow stripe for protective conductor.

Key points

• The phase colors in the convention columns are common practice, not code requirements. Always check the site's posted identification scheme.
• Gray is used for 277/480 V neutrals so they are not confused with white 120/208 V neutrals in the same building.
• Never use white, gray or green for a hot conductor. Re-identifying a white conductor as hot is only permitted in the limited cases the code lists (NEC 200.7).
• Color alone does not prove a conductor is de-energized. Test before touching.

Common mistakes

• Assuming IEC brown, black and gray match US black, red and blue phase by phase on imported equipment.
• Treating "orange means 480 V". In a 4-wire delta system, orange is the high-leg marking.
• Selling only white for jobs that need separate neutrals for two voltage systems.

Governing standards: NEC (NFPA 70) 200.6, 200.7, 210.5, 215.12, 250.119 and 110.15; NFPA 79 for industrial machinery; CSA C22.1 (Canadian Electrical Code); IEC 60445.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.