The standard US NEC color code for 120/208V 3-phase wiring is Black (L1), Red (L2), and Blue (L3), with White for neutral and Green/Bare for ground. For 277/480V systems, the phases shift to Brown, Orange, and Yellow. In contrast, the international IEC standard uses Brown, Black, and Grey for phases, and Blue for neutral. Always verify local code, as the Authority Having Jurisdiction (AHJ) has final say.
The Master 3-Phase Color Code Reference Table
Use this table to identify conductor functions across the most common global and regional standards. Read the 'Phases' columns left-to-right as L1, L2, and L3. Note that while the IEC standard is harmonized across most of Europe and the UK, the US NEC strictly separates color codes by voltage class to prevent catastrophic miswiring.
| Standard / Region | Phase 1 (L1) | Phase 2 (L2) | Phase 3 (L3) | Neutral (N) | Ground (PE) |
|---|---|---|---|---|---|
| US NEC (120/208V) | Black | Red | Blue | White | Green / Bare |
| US NEC (277/480V) | Brown | Orange | Yellow | Gray | Green / Bare |
| IEC (EU / UK Post-2006) | Brown | Black | Grey | Blue | Green-Yellow Stripe |
| Old UK (Pre-2006) | Red | Yellow | Blue | Black | Green |
| US High-Leg Delta (240V) | Black | Orange (Wild) | Red | White (Center Tap) | Green / Bare |
Rows People Get Wrong (and How to Fix Them)
Color codes look simple on paper, but jobsite realities introduce severe hazards if you misinterpret them. Here are the most common failure points and how to handle them.
The 480V Voltage Shift Mistake
The most dangerous mistake in US commercial wiring is using Black, Red, and Blue for a 277/480V system. Electrical Construction & Maintenance (EC&M) frequently highlights this code violation. If a technician assumes Black/Red/Blue means 120V to ground, they will touch a 277V conductor and suffer a lethal shock. NEC Article 215.12 requires Brown, Orange, and Yellow for 480V feeders. If you are pulling 480V wire and the manufacturer only supplies black THHN, you must use 3M Super 33+ phase tape (Brown, Orange, Yellow) at every termination and splice point.
The High-Leg (Wild-Leg) Delta
In older US industrial facilities, you will encounter a 240V 3-phase Delta system with a center-tapped neutral on one winding to provide 120V for control circuits. Phase A to Neutral reads 120V. Phase C to Neutral reads 120V. But Phase B (the 'wild leg' or 'high leg') to Neutral reads 208V (120V × √3). The NFPA 70 National Electrical Code mandates that this high leg must be colored Orange and is typically landed on the B-phase (middle) busbar in the panel. Never land the orange wire on a standard 120V single-pole breaker; it will instantly destroy the connected equipment and trip the breaker.
Safe Interpretation of Faded or Missing Markings
Never trust wire colors in an existing panel built before 1990. UV exposure, heat, and chemical off-gassing turn Red THHN into a pale orange, and Blue into a faded grey. If markings are ambiguous, follow this strict verification protocol:
- De-energize and Lockout/Tagout (LOTO): Shut off the upstream feeder breaker.
- Verify Dead: Use a CAT III or CAT IV multimeter to confirm 0V phase-to-phase and phase-to-ground.
- Energize and Test: Turn the power back on. Measure phase-to-phase. You should read ~208V (or ~480V). Measure phase-to-ground/neutral. You should read ~120V (or ~277V).
- Label: Once identified, wrap the wire ends with fresh, color-coded phase tape and update the panel directory.
Regional Standards and Code Compliance
Understanding which standard applies to your region prevents failed inspections and equipment damage. In the United States, the National Electrical Code (NEC) is the baseline, but local AHJs can amend it. For example, some municipalities require Gray for neutral in all voltage systems to avoid confusion with white 120V neutrals.
In the UK and Europe, the transition to IEC 60446 colors (Brown/Black/Grey) was harmonized in 2006. If you are working in a UK facility built before April 2006, you will likely encounter the old Red/Yellow/Blue scheme. The Institution of Engineering and Technology (IET) advises that when extending old circuits, you must use clear, permanent warning labels at the distribution board to indicate the presence of mixed color codes. Never mix old and new colors in the same multi-core cable without explicit, documented mapping.
If you are wiring a European-manufactured CNC machine or industrial compressor in the US, the internal wiring will use IEC colors (Brown/Black/Grey). Do not rewire the machine. Instead, use an isolating transformer or clearly label the disconnect switch indicating 'IEC Internal Wiring' to protect future maintenance technicians.
Frequently Asked Questions
What is the exact color code for 3 phase 480V wiring in the US?
Under NEC guidelines, 277/480V 3-phase wiring uses Brown for Phase A (L1), Orange for Phase B (L2), and Yellow for Phase C (L3). The neutral conductor must be Gray (to distinguish it from the White neutral used in 120/208V systems), and the equipment grounding conductor is Green or Bare copper. Using Black/Red/Blue for 480V is a severe code violation.
Can I use old UK 3 phase wire colors in a new installation?
No. In the UK, the old Red/Yellow/Blue color code was officially retired in 2006 to align with European IEC standards. Any new installation, or any significant extension to an existing circuit, must use the modern Brown/Black/Grey phase colors and Blue for neutral. If you are tying into an old board, you must place prominent warning notices on the enclosure to alert workers to the mixed color schemes.
How do I safely identify 3 phase wires if the insulation colors are faded?
Do not guess. Faded THHN insulation is a major shock hazard. Use a CAT-rated digital multimeter to measure the voltage between the unknown conductors. Phase-to-phase should read your system voltage (e.g., 208V or 480V). Then, measure each phase to a known ground or neutral. The phase that reads 120V (or 277V) is your live phase. If you find a phase that reads 208V to neutral on a 240V Delta system, you have found the Orange 'high leg'. Once verified, apply fresh phase identification tape at both ends of the conductor.
What does the orange wire mean in a 3 phase panel?
In a standard US 277/480V wye system, Orange is simply Phase B (L2). However, in a 240V Delta high-leg system, the Orange wire designates the 'wild leg' or 'high leg'. This specific conductor has a higher voltage to ground (208V) compared to the other two phases (120V to ground). It must always be landed on the B-phase busbar and should never be connected to a standard line-to-neutral 120V load, as doing so will overvoltage and destroy the equipment.
