In the US and Canada (NEC), black, red, and blue are hot, white and gray are neutral, and bare or green are ground. In Europe and most of the world (IEC), brown, black, and gray are hot, blue is neutral, and green-and-yellow is ground. Because guessing a wire's function based on faded insulation or legacy standards can result in a fatal shock or a burned-out appliance, you must verify the governing code before touching a terminal.
The Master Electric Wire Color Code Chart
The table below maps the exact insulation colors required by the three major wiring standards. Use this as your primary reference when identifying conductors in a junction box, subpanel, or appliance whip.
| Conductor Function | NEC (US & Canada) | IEC (Europe / Global) | Old UK (Pre-2004) |
|---|---|---|---|
| Line 1 (Single Phase Hot) | Black | Brown | Red |
| Line 2 (Split/3-Phase Hot) | Red | Black | Yellow |
| Line 3 (3-Phase Hot) | Blue | Gray | Blue |
| Neutral (Grounded) | White or Gray | Blue | Black |
| Earth / Equipment Ground | Bare, Green, or Green/Yellow | Green/Yellow | Green |
| Switch Leg / Traveler | Any color except White/Green/Bare* | Any color except Blue/Green-Yellow* | Any except Green |
*NEC Article 200.7 strictly prohibits using white or gray for ungrounded (hot) conductors unless permanently re-identified with paint or tape at both ends. IEC similarly protects blue and green/yellow.
Regional Standards: Which Code Governs Your Panel?
The color of a wire only means something if you know which standard the installer was following. A black wire in a New York apartment is a 120V hot; a black wire in a London flat built in 1995 is a neutral.
NEC (NFPA 70) - United States & Canada
The National Electrical Code (NEC) governs North America. The most critical nuance here is voltage-dependent color coding for commercial and industrial 3-phase systems. In a standard 120/208V wye system, phases are Black, Red, and Blue. However, in a 277/480V system, the NEC requires phases to be Brown, Orange, and Yellow, while the neutral becomes Gray. This prevents an electrician from accidentally wiring a 120V receptacle to a 277V lighting circuit. For residential split-phase (120/240V), you will almost exclusively see Black (Line 1), Red (Line 2), White (Neutral), and Bare/Green (Ground).
IEC 60446 - Europe, UK, Australia, New Zealand
The International Electrotechnical Commission standard is used by most of the globe. In 2004, the UK harmonized its colors with the IEC to match mainland Europe. If you are working in a UK home built before 2004, you will encounter the 'Old UK' column: Red (Live), Black (Neutral), and Green (Earth). If you are working in a post-2004 UK home, it follows the IEC: Brown (Live), Blue (Neutral), and Green/Yellow (Earth). Always check the consumer unit (breaker box) for a warning label indicating mixed color codes, which is legally required in the UK during the transition period.
The 'Rows People Get Wrong' & Faded Wire Protocols
Even when you know the standard, real-world jobsite conditions and specific wiring methods create exceptions that catch DIYers off guard.
Rows and Scenarios People Get Wrong
- The 'Switch Loop' White Wire: In older NEC wiring, power was sent down to a light switch on a 2-wire cable. The white wire was used as the 'hot' feed down to the switch, and the black wire was the 'switch leg' returning power to the light. The Mistake: People assume the white wire is neutral and touch it while the breaker is on. The Code: NEC 200.7(C)(1) requires the white wire in a switch loop to be permanently re-identified with black or red tape at both ends. If you see an untaped white wire connected to a brass screw on a switch, treat it as a 120V hot.
- 3-Way Switch Travelers: The NEC does not mandate a specific color for traveler wires running between two 3-way switches. While red and black are best practice, you will frequently see white, blue, or even yellow used as travelers. Never assume a traveler is a neutral just because it is white.
- High-Leg Delta (Wild Leg): In older commercial 240V 3-phase delta systems, the 'high leg' (which measures 208V to ground instead of 120V) must be identified by Orange insulation. If you land a standard 120V circuit on the orange phase, you will instantly destroy the connected equipment.
Safe Interpretation Protocol for Faded or Missing Markings
THHN insulation fades under UV exposure, and old rubber-coated wiring (common in pre-1960s homes) often cracks and loses its color entirely. When you cannot confidently identify a wire by sight, follow this bench-and-jobsite proven protocol:
- Initial NCVT Sweep: With the breaker ON, use a Non-Contact Voltage Tester (NCVT) to identify which wires are energized. Mark them with a piece of tape. Note: NCVTs can give false positives from phantom voltage in parallel runs, so this is only step one.
- De-energize and Isolate: Turn off the breaker. Verify it is dead. Disconnect the questionable wires from their terminals so they are floating and not tied into a load.
- Multimeter Continuity & Resistance: Turn the breaker back ON (keep bare hands clear of exposed copper). Set your multimeter to AC Voltage. Measure Hot-to-Neutral (should read 114V-126V). Measure Hot-to-Ground (should read 114V-126V). Measure Neutral-to-Ground (should read < 2V). The wire that yields < 2V when paired with your known hot is your neutral.
- Permanent Re-identification: Once identified, do not rely on memory. Wrap the wire with OSHA-compliant 3M Scotch 35 Series electrical tape (which is rated for 600V and won't leave a gooey residue like cheap vinyl tapes), or slide a piece of color-coded heat shrink tubing over the end before terminating it to the lug.
When in doubt, pull a new wire. The cost of a 500-foot spool of 12 AWG THHN is roughly $120—a small price to pay to avoid a miswired neutral that could energize your plumbing or cause a neutral-to-ground fault that trips your main GFCI breaker endlessly.
