The correct color code for voltage depends entirely on your region's governing electrical standard and the specific nominal voltage of the system. In North America (NEC), 120/208V three-phase systems use Black, Red, and Blue for phases, while 277/480V systems step up to Brown, Orange, and Yellow. In Europe and the UK (IEC 60446), 230/400V systems universally use Brown, Black, and Grey. Never assume a wire's function by its jacket color alone; always verify with a CAT III or CAT IV multimeter before making contact.
Master Wire Color Code for Voltage Reference Chart
The table below maps the standard phase, neutral, and ground conductor colors across the most common commercial and industrial voltage systems. This chart aligns with the NFPA 70 (National Electrical Code) for North America and IEC 60446 for international harmonized regions.
| Standard / Region | System Voltage | Phase 1 (L1) | Phase 2 (L2) | Phase 3 (L3) | Neutral | Ground |
|---|---|---|---|---|---|---|
| NEC (US/Canada) | 120/208V (3-Phase Wye) | Black | Red | Blue | White / Grey | Green / Bare |
| NEC (US/Canada) | 120/240V (Split-Phase) | Black | Red | N/A | White / Grey | Green / Bare |
| NEC (US/Canada) | 277/480V (3-Phase Wye) | Brown | Orange | Yellow | Grey | Green / Bare |
| IEC (EU / UK / AU) | 230/400V (3-Phase) | Brown | Black | Grey | Blue | Green/Yellow Stripe |
| Old UK (Pre-2004) | 240/415V (3-Phase) | Red | Yellow | Blue | Black | Green |
Regional Variants and the 'Rows People Get Wrong'
While the chart above covers standard installations, real-world jobsites are full of edge cases, legacy wiring, and specific high-voltage configurations that trip up even experienced techs. Here is how to interpret the most dangerous variations and what to do when the colors lie.
In older US industrial facilities, you will encounter 240V Delta High-Leg systems. This setup provides 240V three-phase for motors, but uses a center-tapped transformer winding to provide 120V for standard outlets. Phase A to Neutral is 120V, and Phase C to Neutral is 120V. However, Phase B (the high leg) measures 208V to ground. NEC Article 210.5(C) strictly mandates that this high-leg conductor must be colored Orange (or tagged with orange tape). If you mistakenly land this orange wire on a standard single-pole 120V breaker, you will feed 208V directly into a 120V circuit, instantly destroying the connected load and creating a severe fire hazard.
277V Lighting vs. 480V Power Confusion
A common mistake in commercial buildings is assuming that Brown, Orange, and Yellow THHN wires are exclusively used for 480V heavy machinery. In reality, these are the exact same colors used for 277V single-phase lighting circuits derived from a 480V wye transformer. When pulling wires for a 277V lighting contactor, you will typically use Brown (or Orange/Yellow) as the hot and Grey as the neutral. Always verify the voltage at the termination point; a 480V motor and a 277V LED driver might share the same conduit, but their breaker sizing and termination torques are vastly different.
Safe Interpretation of Faded or Missing Markings
UV exposure, heat, and age cause THHN and XHHW-2 insulation to fade. A black wire might look dark grey, and a red wire might fade to a pale orange, leading to catastrophic misidentification. If you encounter faded wires or unmarked conductors in a legacy panel:
- De-energize and Lockout/Tagout (LOTO): Shut off the main feed and verify it is dead using a non-contact voltage tester, followed by a live-dead-live test on a known source with your multimeter.
- Test Phase-to-Ground and Phase-to-Neutral: Re-energize the upstream feed (if safe to do so for testing) and use a CAT III 1000V rated meter (like a Fluke 87V or T6-1000). Measure the voltage from the mystery wire to the ground bus, then to the neutral bus. A 120V reading to neutral on a 208V system confirms it is a phase conductor.
- Re-identify Per Code: Once verified, NEC 200.7 requires you to permanently re-identify the wire at every termination point. Do not use cheap electrical tape that unspools in hot panels. Use high-quality vinyl tape (like 3M Super 33+) or adhesive-lined heat shrink tubing to mark the correct phase color.
For deeper guidance on international harmonization and legacy transitions, the UK Health and Safety Executive (HSE) provides excellent documentation on transitioning from old regional colors to modern IEC standards.
Frequently Asked Questions
What is the standard color code for 240V voltage?
It depends on whether the 240V system is single-phase (split-phase) or three-phase. In a standard US residential split-phase 120/240V system, the two hot legs are Black and Red, the neutral is White, and the ground is Bare/Green. However, in a commercial 240V three-phase Wye system (common in parts of Canada and specific US industrial setups), the phases are Black, Red, and Blue. In IEC regions, a 240V single-phase circuit uses Brown for the hot leg and Blue for the neutral.
Does the color code for voltage change for DC circuits?
Yes, DC circuits follow different conventions because there are no alternating phases. For standard ungrounded DC systems (like a 12V or 24V solar battery bank or automotive setup), Red is the positive (+) conductor and Black is the negative (-) conductor. However, for grounded DC power systems (like telecom -48V setups or industrial control circuits), the NEC dictates different rules: the grounded conductor (often the positive in telecom, or negative in standard DC) must be White or Grey, and the ungrounded conductor is typically Red or Blue. Always check the specific system schematic, as telecom and industrial DC polarity conventions frequently conflict.
How do I identify voltage wire colors on unmarked or faded THHN?
Never guess based on a faded jacket. If a wire's color is compromised, treat it as an unknown energized conductor. First, isolate the circuit and perform a continuity test from the wire in question to the neutral and ground buses to rule out it being a neutral or ground. If it shows continuity to ground, it is a ground. If it shows open-line (infinite resistance) to both neutral and ground, it is a hot or a switched leg. Once identified, you must physically re-identify the wire at both ends and at every accessible junction box using colored phasing tape or heat shrink, as mandated by NEC Article 210.5(C) for branch circuits and 215.12 for feeders.
