In the US (NEC), black and red are hot, white and gray are neutral, and bare or green are ground. In the IEC (Europe and modern UK), brown is hot, blue is neutral, and green-and-yellow is ground. Because guessing wire functions can lead to catastrophic shorts or fatal shocks, you need a reliable reference before stripping insulation or terminating lugs.

The Master Electric Wires Color Code Reference

The table below maps the standard electric wires color code across the major global regions and system types. Use this as your primary bench and jobsite reference.

Function US AC (NEC 120/240V) US DC (Standard) IEC AC (EU / Modern UK) IEC DC
Hot / Phase 1 (L1) Black Red or Black Brown Brown
Hot / Phase 2 (L2) Red Yellow (or Black w/ Red trace) Black Grey
Hot / Phase 3 (L3) Blue Blue (or Black w/ Blue trace) Grey Blue
Neutral (N) White or Grey White or Grey Blue Blue (with white trace)
Ground (PE) Green, Green/Yellow, or Bare Green or Bare Green with Yellow Stripe Green with Yellow Stripe
High-Leg Delta (Wild Leg) Orange N/A N/A N/A

Regional Variants and the 'Rows People Get Wrong'

While the table above covers modern standards, legacy systems and specific code exceptions cause the most mistakes on the jobsite. If you are working in a home built before 2006 in the UK, or an older commercial building in the US, the electric wires color code will differ.

Old UK vs. Modern UK (IEC Harmonization)

Prior to April 2006, the UK used a distinct color code: Red for live, Black for neutral, and Green/Yellow (or bare) for earth. When the UK harmonized with the IEC 60446 standard, live became Brown and neutral became Blue. If you open a UK junction box and see red and black THHN or twin-and-earth flex, you are looking at pre-2006 wiring. Treat the red as your brown (hot) and the black as your blue (neutral). Electrical Safety First provides excellent visual guides for identifying these mixed-generation UK circuits.

The Rows People Get Wrong (And Why They Trip Breakers)

  • White as a Hot Wire (Switch Loops): Under NEC 200.7(C)(1), a white wire can be used as an ungrounded (hot) conductor in a cable assembly (like NM-B) only if it is permanently re-identified with black or red phase tape at both ends. People constantly forget to tape the white wire in 3-way switch travelers or switch loops, leading to the next electrician assuming it is a neutral and creating a dead short.
  • The High-Leg Delta (Orange): In a 120/240V 3-phase delta system, two legs yield 120V to neutral, but the 'wild leg' yields 208V to neutral. NEC 110.15 mandates this leg must be Orange (or high-leg delta orange). If you misidentify this wire as a standard 120V phase and wire it to a standard receptacle, you will instantly fry any 120V appliance plugged into it.
  • DC Grounded vs. Ungrounded: In standard DC, white is the grounded (negative) conductor. However, in 48V telecom and some solar arrays, the system is positive-grounded. In these setups, the white wire might actually be the positive hot, while the black wire is the grounded negative. Always verify DC polarity with a multimeter; never trust the jacket color blindly on legacy telecom racks.
⚠️ Code Caveat: The National Electrical Code (NEC) provides the baseline for US wiring colors, but local Authorities Having Jurisdiction (AHJ) may have specific amendments regarding phase tape colors or conduit color-coding. Always defer to your local inspector for final compliance.

Safe Interpretation When Markings Are Faded or Missing

On the bench or in a hot attic, THHN insulation degrades. Red wire fades to a pale pink or orange, and black wire can look dark brown. Older cloth-covered wiring from the 1940s often turns entirely yellow or brittle brown, making the original electric wires color code impossible to read visually.

When you cannot trust the jacket color, you must rely on systematic electrical testing. Never assume a wire is neutral just because it looks white; a shared neutral carrying unbalanced current from a multi-wire branch circuit (MWBC) can carry lethal voltage if the breaker is only half-off.

The Faded Wire Verification Protocol

  1. De-energize and Lock Out: Turn off the main breaker or the specific branch circuit breaker. Use a lockout/tagout (LOTO) device if you are not standing directly over the panel.
  2. Verify Dead with a CAT III/IV Meter: Do not rely solely on a non-contact voltage tester (NCVT) like a Klein NCVT-4 for the final check. NCVTs can miss shielded voltages or give false positives from phantom coupling. Use a Fluke 117 or equivalent CAT III multimeter. Test Hot-to-Ground, Hot-to-Neutral, and Neutral-to-Ground. All must read 0.0V.
  3. Continuity Testing for Neutrals and Grounds: With power confirmed dead, set your meter to continuity (the diode/beep setting). Test the suspected neutral to the known grounding bus bar. It should beep (read less than 1 ohm). Test the suspected ground to the grounding bus bar; it should also beep. If both beep, you must trace the circuit back to the panel to identify which is the current-carrying neutral and which is the equipment grounding conductor (EGC).
  4. Re-Identify Immediately: Once verified, wrap the ends of the wire with 3M Super 33+ vinyl electrical tape in the correct color. Do not use cheap PVC tape; it unwraps in hot panels and leaves a sticky residue that ruins the insulation over time.

Frequently Asked Questions

Can I use a white wire as a hot wire in a standard outlet?

Yes, but only under specific conditions outlined in NEC 200.7(C). If you are running a switch loop or wiring a 3-way switch using a 2-conductor cable (like 14/2 NM-B), the white wire must carry the switched hot or the traveler. You are legally required to permanently re-identify this white wire at both the switch and the panel using black or red phase tape, or permanent marker. If you leave it white, the next person working on the circuit may assume it is a neutral and create a severe shock hazard.

What color is the ground wire in a 3-core flexible appliance cable?

It depends on the region and the standard the cord was manufactured to. In the US (UL standard SJT/SVt cords), the ground wire is almost always Green. In the UK and Europe (IEC harmonized H05VV-F cords), the ground wire is strictly Green with a Yellow Stripe. If you are replacing a plug on an imported appliance and see a green/yellow wire, that is your earth/ground connection. Never wire a green/yellow wire to a hot or neutral terminal.

Why does my white neutral wire have 120V on my non-contact tester?

If your non-contact voltage tester (NCVT) beeps when held near a white neutral wire, you are likely seeing 'phantom voltage' caused by capacitive coupling from an adjacent hot wire in the same cable, or you have an 'open neutral' fault. To diagnose, use a standard multimeter. Measure the voltage between the white wire and a known good ground. If it reads near 120V, your neutral is broken or disconnected somewhere upstream (an open neutral), which is a severe fire hazard because it causes unbalanced voltages on MWBCs. If the multimeter reads 0V to 2V, but the NCVT still beeps, it is just harmless phantom coupling; the neutral is intact.