The direct answer for North American (NEC) AC wiring is: Black or Red for hot, White for neutral, and Bare or Green for ground. For international (IEC) wiring, the standard is: Brown or Black for hot, Blue for neutral, and Green-and-Yellow for ground. Never assume a wire's function by its color alone without verifying with a meter, especially in older buildings, retrofits, or imported machinery.
The Master AC Color Code Reference Table
Below is the definitive cross-reference for AC power conductor colors across the three major global standards. Use this table to identify wires in fixed building wiring (NM-B, THHN) and flexible appliance cords.
| Function | US & Canada (NEC / CEC) | Europe & UK (IEC 60445) | Australia & NZ (AS/NZS 3000) |
|---|---|---|---|
| Protective Earth (Ground) | Bare, Green, or Green/Yellow | Green-and-Yellow (Striped) | Green/Yellow (Striped) |
| Neutral | White or Grey | Blue | Black (or Light Blue) |
| Single-Phase Hot (Line) | Black (or Red) | Brown | Red (or Brown) |
| Split-Phase Hot 2 | Red | N/A (Black used for 3-phase) | N/A |
| 3-Phase Hot 1 (L1) | Black (or Brown) | Brown | Red (or Brown) |
| 3-Phase Hot 2 (L2) | Red (or Orange/Black) | Black | White (or Black) |
| 3-Phase Hot 3 (L3) | Blue (or Yellow/Black) | Grey | Blue (or Grey) |
| High-Leg Delta (US Only) | Orange | N/A | N/A |
Regional Standards: NEC vs. IEC vs. Old UK
Wire color codes are strictly governed by regional electrical safety authorities. Mixing these standards in a single panel is a severe shock and fire hazard.
US & Canada (NEC Article 310.12 & CEC): The National Electrical Code (NFPA 70) mandates White/Grey for grounded (neutral) conductors and Bare/Green for equipment grounding conductors. Hot wires can be any color except white, grey, or green. In standard 120V/240V residential NM-B cable, you will almost exclusively see Black (Hot), White (Neutral), and Bare (Ground).
Europe & Modern UK (IEC 60445): The IEC 60445 standard harmonized European colors in 2004. Earth is strictly Green/Yellow. Neutral is strictly Blue. Single-phase line is Brown. Three-phase lines are Brown, Black, and Grey.
The Old UK Trap (Pre-2004): If you are working in a UK home built before 2004, you will encounter the old color code: Red for Live (Hot), Black for Neutral, and bare/green for Earth. This is the exact opposite of the modern US standard (where Black is hot and White is neutral). Treating an old UK black wire as a US-style hot wire will result in a direct short or fatal shock. Always test old UK circuits with a multimeter before touching them.
The "Rows People Get Wrong" Trap
Even when you know the standard, specific edge cases and code exceptions trip up experienced DIYers and junior electricians. Here are the most common misidentifications:
- The "Blue" Trap (US vs EU): In the US, Blue is frequently used as a hot leg in 277V/480V commercial panels or as a traveler in 3-way switches. In Europe, Blue is strictly the Neutral wire. If you wire a US-style blue hot leg into an imported EU machine expecting a blue neutral, you will send 277V or 480V directly into the machine's neutral bus, causing catastrophic component failure and arc flash.
- White Wire Used as Hot (Switch Loops): Under NEC 310.12(A)(1), a white wire can be used as a hot wire in a switch loop only if it is permanently re-identified with black or red electrical tape (or paint) at every termination point. The most common mistake is finding a white wire connected to a switch, assuming it's a neutral, and touching it. Always check for re-identification tape inside the back of the junction box.
- The High-Leg Delta (Orange): In older US commercial buildings with 120/240V 3-phase Delta service, the B-phase (high leg) measures 208V to ground instead of 120V. OSHA 1910.304 and NEC 110.15 require this leg to be colored Orange. If you land a standard 120V appliance on the orange leg and the neutral, you will instantly fry the appliance and trip the breaker.
- Grey vs. White Neutrals: While both are legal neutrals in the US, grey THHN is typically reserved for 277V/480V systems to prevent mixing up the neutrals of different voltage systems in a shared conduit. Do not use grey for standard 120V residential branch circuits.
Decision Tree: Identifying Faded, Missing, or Foreign Wires
When working in older homes, painted-over junction boxes, or conduit pulls where the THHN insulation is faded or non-standard, never trust the color. Use this diagnostic sequence to safely identify conductors. You will need a Non-Contact Voltage Tester (NCVT) like the Klein NCVT-3 and a True-RMS Digital Multimeter like the Fluke 117.
| Symptom / Condition | Diagnostic Action | Required Tool | Concrete Next Step |
|---|---|---|---|
| Wire color is completely faded, painted, or covered in drywall mud. | Turn off main breaker. Strip 1/2" of insulation. Perform continuity test between unknown wire and known ground bus. | Multimeter (Continuity/Ohms mode) | If continuity reads < 1 ohm, mark wire with green tape (Ground). If OL (open loop), proceed to next step. |
| Multiple unmarked wires remain after identifying ground. | Re-energize panel safely. Scan each wire with NCVT from 1 inch away. | NCVT (e.g., Klein NCVT-3) | Wires that beep/flash red are Hot (Line). Mark with black tape. Wires with no response are likely Neutral. Proceed to verify. |
| NCVT identifies a Hot wire, but you need to confirm the Neutral among remaining dead wires. | Set meter to AC Voltage (V~). Measure between the confirmed Hot wire and each unknown wire. | Digital Multimeter (e.g., Fluke 117) | The wire that reads 120V (or 230V in EU) relative to the Hot wire is your Neutral. Mark with white (US) or blue (EU) tape. |
| Meter reads 0V between Hot and suspected Neutral, but NCVT shows no voltage on the suspected neutral. | Measure voltage between suspected Neutral and known Ground bus. | Digital Multimeter | If reading is 0V to ground, it is confirmed Neutral. If reading is ~120V to ground, you have a broken neutral or a miswired hot leg. De-energize and trace the circuit. |
Final Verdict & Default Recommendations
Stop guessing and standardize your workbench and panel. The correct wire color depends entirely on your region and the specific cable type you are pulling. Here is exactly what to buy and use for new installations:
- For US/Canada Residential Branch Circuits: Buy standard NM-B (Romex) cable. It comes pre-jacketed with Black (Hot), White (Neutral), and Bare (Ground). For conduit pulls, buy individual THHN/THWN-2 conductors in Black, White, and Green.
- For EU/UK Fixed Wiring & Appliance Cords: Buy standard H07V-K (single core) or H05VV-F (flexible cord). Use Brown for Live, Blue for Neutral, and Green/Yellow for Earth. Never use solid green for earth in an IEC region; it must be striped.
- For US 240V Split-Phase (Dryers/Ranges): Use 10/3 or 6/3 NM-B, which provides Black (Hot 1), Red (Hot 2), White (Neutral), and Bare (Ground).
- The Golden Rule: If you are integrating imported machinery (e.g., a European 230V pump) into a US 240V panel, physically remove the IEC Blue/Black/Brown flex cord and replace it with US-coded THHN or NM-B before it enters the US junction box. Never transition IEC colors directly into a US NEC panel without clear, physical labeling and re-termination.
