In the US and Canada (NEC standard), black and red are hot, white and gray are neutral, and bare or green are ground. In Europe and the UK (IEC standard), brown is hot, blue is neutral, and green-yellow is ground. However, assuming a wire's function based purely on its jacket color is a leading cause of arc flashes and miswired circuits. This reference guide provides the exact color codes across global standards, highlights the specific rows where DIYers and apprentices make dangerous assumptions, and gives you a concrete decision path for dealing with faded, painted, or unmarked conductors.

The Master Wire Color Code Reference Table

This table covers standard AC mains wiring. It assumes copper conductors in standard residential and light commercial environments. Always verify with a meter before touching any conductor, regardless of the jacket color.

Function US / Canada NEC (120/208/240V) US / Canada NEC (277/480V 3-Phase) IEC 60446 (EU, UK, AU, NZ) Old UK (Pre-2006)
Line 1 (Hot/Phase) Black Brown Brown Red
Line 2 (Hot/Phase) Red Orange Black Yellow
Line 3 (Hot/Phase) Blue Yellow Grey Blue
Neutral White or Grey Grey Blue Black
Earth / Ground Bare, Green, or Green-Yellow Green or Green-Yellow Green-Yellow Green-Yellow

Regional Variants: NEC vs. IEC vs. Old UK

Wire color codes are strictly governed by regional electrical codes. Applying the wrong regional standard to an existing installation is a critical safety hazard.

  • NEC (National Electrical Code / NFPA 70): Applies to the United States and heavily influences Canada (CEC). The NFPA 70 standard dictates the black/red/blue and white/gray scheme for standard 120/240V split-phase and 120/208V three-phase systems. Note that the NEC does not strictly mandate the color of the 'hot' wire in a single-phase circuit (it just mandates the neutral must be white/gray and ground must be green/bare), but black is the universal industry default.
  • IEC 60446 (International Electrotechnical Commission): Adopted across the European Union, Australia, New Zealand, and the UK (post-2006). The harmonized colors are brown (hot), blue (neutral), and green-yellow (earth). If you are wiring a new circuit in these regions, this is the only legal standard.
  • Old UK Colors (Pre-2006): Before the UK harmonized with the IEC in 2006, the standard was red (hot), black (neutral), and green (earth). You will still encounter these in homes built before the mid-2000s. Warning: The old UK black wire is a neutral, but in the modern IEC standard, black is a hot phase. Mixing up old and new UK wiring in a junction box is a fatal mistake.
High-Leg Delta Warning: In the US, 240V 3-phase High-Leg Delta systems use Orange for the 'high leg' (which carries 208V to neutral instead of 120V). NEC 110.15 requires this high leg to be distinctly marked, and Orange is the mandated color. Never wire a standard 120V load to an orange wire in a commercial panel.

The "Rows People Get Wrong" Trap

Even when you know the standard, specific real-world applications bend the rules. Here are the most common misinterpretations that lead to shocked DIYers and failed inspections.

1. The White Wire Used as a Hot (Switch Loops)

In older residential wiring, 2-wire NM-B (Romex) was often run from a ceiling fixture down to a wall switch. The black wire carries hot down to the switch, and the white wire carries the switched hot back up to the light. In this scenario, the white wire is hot. According to NEC 200.7(C)(2), this white wire must be re-identified with black tape or permanent marker at both ends to indicate it is being used as an ungrounded (hot) conductor. If you see a white wire connected to a brass screw on a switch or a black pigtail in a wire nut bundle, assume it is hot until proven otherwise.

2. Grey in 277/480V Systems

In standard 120/240V residential wiring, grey is rarely used. But in commercial 277/480V 3-phase panels, grey is the neutral. Apprentices frequently confuse the 277/480V hots (Brown, Orange, Yellow) with the 120/208V hots (Black, Red, Blue). If you are working in a commercial panel and see a grey wire, do not treat it as a phase conductor; it is the grounded neutral carrying unbalanced current.

3. Green vs. Bare vs. Green-Yellow

While all three signify an equipment grounding conductor (EGC) under the NEC, you cannot mix and match them arbitrarily in conduit. If you pull insulated green wires for your ground in a conduit run, you must use green for the entire run. You cannot splice a bare copper ground to an insulated green wire inside a junction box without a proper mechanical connector, and the AHJ (Authority Having Jurisdiction) may flag it as a violation of NEC 250.119.

Decision Path: Identifying Faded, Painted, or Unmarked Wires

Jacket colors fade under UV exposure, get painted over by careless drywallers, or pull through dirty conduits. When visual identification fails, use this decision tree to safely identify the conductor and terminate the task with a permanent fix.

Condition Immediate Action Tool / Part Pick
Wire is painted over Do not guess. Scrape exactly 1 inch of paint off the jacket near the panel and the device box to reveal the original color. Klein Tools 11055 Wire Stripper (use the non-cutting scraping notch).
Colors are faded/dirty Wipe with isopropyl alcohol. If the distinction between black and dark grey is still ambiguous, treat it as an unknown hot. Fluke T6-1000 Electrical Tester (use the non-contact volt-alert and open-jaw voltage check).
Wire is completely unmarked (conduit pull) De-energize the circuit. Use a tone generator to trace the physical path from panel to box. Ring it out with a multimeter for continuity. Fluke IntelliTone Pro 200 + Fluke 117 True-RMS Multimeter.
Final Step: Re-identification Once verified, permanently label the wire at both ends. Do not rely on electrical tape, which dries out and falls off after 3-5 years. Concrete Pick: Brother PT-D210 Label Maker with TZe-231 (Black on White, 12mm) laminated vinyl tape.
Pro-Tip for Switch Loops: If you are replacing an old switch loop and the white wire is being used as a hot, wrap it with 3M Super 33+ vinyl electrical tape. Wrap it completely around the circumference at least twice, extending 1 inch past the stripped end. Better yet, use a heat-shrink tubing sleeve (3/16 inch, black) shrunk over the end before terminating.

Safe Interpretation and Verification Protocol

Never trust color coded wires electrical wiring without independent verification. The OSHA electrical safety guidelines and NFPA 70E mandate treating all conductors as energized until proven dead. Follow this exact Live-Dead-Live testing protocol before making any connections or cuts.

  1. De-energize and Lockout: Turn off the breaker. If you are not at the main panel, use a lockout/tagout device on the breaker handle to prevent someone from flipping it back on while you are working.
  2. Verify Your Meter: Test your multimeter or non-contact voltage tester (NCVT) on a known live circuit (like an adjacent outlet). Confirm it reads ~120V (or ~230V in IEC regions).
  3. Test the Target Circuit: Place your meter probes on the suspected hot and the known ground/neutral. The reading must be 0.0V. Test Line-to-Neutral, Line-to-Ground, and Neutral-to-Ground.
  4. Re-verify Your Meter: Test your meter on the known live circuit again. This ensures your meter didn't blow its internal fuse or lose battery power during step 3, which would give you a false 'dead' reading.

By combining the master reference table with a strict verification protocol and permanent labeling, you eliminate the guesswork that causes residential fires and commercial downtime. When in doubt, trace it, test it, and label it.