The modern standard for European wiring colour codes is defined by IEC 60446 (adopted in the UK as BS 7671 Amendment 2). If you are working on any installation built or rewired after April 2006 in Europe or the UK, the harmonised colours apply universally. Single-phase line is brown, neutral is blue, and earth is green-and-yellow. Do not guess based on old habits or US standards; misidentifying a conductor in a 230V/400V system will result in catastrophic short circuits or lethal shock.

The Harmonised European Wiring Colour Code Chart (IEC 60446)

This is your primary reference for any post-2006 EU or UK domestic and commercial installation. Keep this table accessible when terminating sockets, isolators, or consumer units.

Function Single-Phase Colour 3-Phase Colour IEC 60446 Ref Practical Meaning in the Field
Protective Earth (PE) Green & Yellow Green & Yellow Clause 5.3.2 Safety ground path. Must never carry load current. Continuity to main earthing terminal is mandatory.
Neutral (N) Blue Blue Clause 5.3.3 Current return path. Nominally 0V relative to earth, but must always be treated and isolated as a live conductor.
Line 1 (L1) Brown Brown Clause 5.3.4 Active phase conductor. Carries 230V AC RMS relative to Neutral/Earth in single-phase setups.
Line 2 (L2) N/A Black Clause 5.3.4 Second phase in 3-phase systems. Carries 400V AC RMS relative to L1 or L3.
Line 3 (L3) N/A Grey Clause 5.3.4 Third phase in 3-phase systems. Carries 400V AC RMS relative to L1 or L2.
Warning: Never assume a blue wire is safe to touch. In a multi-wire branch circuit or 3-phase setup, a disconnected neutral can rise to full phase voltage (230V) due to unbalanced loads or induced voltages. Always test before touching.

Regional & Historical Variants: Old UK vs. Modern EU vs. US NEC

The most dangerous scenario for an electrician or DIYer is opening a junction box in a pre-2006 UK property or working on imported US equipment. The UK transitioned from its traditional colours to the European harmonised colours in 2004, with a mandatory cutoff for new installs in 2006. Meanwhile, the US NEC (NFPA 70) uses an entirely different schema.

Function Modern EU / UK (Post-2006) Old UK (Pre-2004) US NEC (120/240V Split)
Earth / Ground Green & Yellow Green (or bare) Green, Yellow-Green, or Bare
Neutral Blue Black White or Grey
Line / Hot (Single) Brown Red Black or Red
L1 (3-Phase) Brown Red Black (or Brown in 208V)
L2 (3-Phase) Black Yellow Red (or Orange in 208V)
L3 (3-Phase) Grey Blue Blue (or Yellow in 208V)

The 'Rows People Get Wrong' Field Notes

When transitioning between standards or dealing with mixed-age installations, specific colour swaps cause the majority of faults and shocks. Memorise these three pitfalls:

  • The 'Black' Trap in 3-Phase EU: In the US, black is a standard hot wire, and in the old UK system, black was the neutral. In the modern harmonised EU 3-phase system, black is Line 2 (L2). If you treat a black wire in a modern European 3-phase industrial panel as a neutral or a safe wire, you will make contact with 400V.
  • The 'Blue' Trap in Old UK 3-Phase: If you are retrofitting an old UK 3-phase motor or distribution board, the old L3 conductor was blue. Today, blue is strictly Neutral. Connecting a modern blue neutral pigtail to an old blue L3 phase will instantly short the system or energise the neutral bar to 400V.
  • Switched Lives and Interconnects: In lighting circuits, the wire returning from a switch to the light fitting (the switched live) is technically a line conductor. In modern EU wiring, this is typically a brown wire, but it is often a blue wire (from a 3-core-and-earth cable) that must be sleeved brown at both ends. If you see an unsleeved blue wire connected to a light switch terminal, it is a switched live, not a neutral.
Pro Tip: Keep a roll of brown, blue, and green/yellow heat-shrink sleeving and PVC electrical tape in your pouch. If you encounter a switched live that hasn't been properly marked with brown sleeving, sleeve it immediately before terminating. Electrical Safety First strongly advises against relying on unmarked conductors in domestic lighting loops.

Decision Path: Identifying Unmarked, Faded, or Mixed Wires

Colours fade, painters tape over junction boxes, and previous DIYers use whatever wire was left in the van. When visual identification fails, follow this strict decision tree to identify the conductor's function safely.

Condition / Observation Immediate Action Final Resolution (Concrete Pick)
Wire insulation is painted over, heavily oxidised, or completely missing. Isolate circuit at the breaker. Do not attempt to scrape paint while live. Strip back to clean copper. Apply 600V rated heat-shrink tubing in the correct IEC colour based on continuity testing (see below).
Circuit is dead. Testing continuity between mystery wire and main earth bar. Use multimeter in continuity mode. Read < 1.0 Ω. Identify as Protective Earth (PE). Sleeve with Green/Yellow and terminate only to earth blocks.
Circuit is dead. Continuity to earth is infinite (OL). Testing continuity to known neutral bus. Use multimeter. Read < 1.0 Ω to neutral bus, OL to line bus. Identify as Neutral (N). Sleeve with Blue and terminate to neutral bar.
Circuit is LIVE. Wire shows ~230V to earth/neutral, but colour is wrong (e.g., black in a single-phase socket). Use CAT III/IV meter to verify voltage to known earth. Do not rely on non-contact testers. Identify as Line (L1). Sleeve with Brown, label the circuit at the consumer unit as 'Non-Standard Colours Used'.
Wire is Blue, but connects to a switch terminal or shows 230V when the switch is closed. Verify voltage state with switch toggled. Confirmed as switched live. Sleeve both ends with Brown (or apply brown tape flags). Never terminate to the neutral bar.

Safe Testing Protocol for Unknown Circuits

When the decision path above requires live testing, you must follow a verified safe isolation and testing procedure. Relying on wire colour alone is a violation of BS 7671 Regulation 132.14 and basic electrical safety principles.

  1. Prove your meter: Before touching any wire, test your multimeter or voltage indicator on a known live source (like a proving unit or a verified live socket) to confirm the meter is functioning and the battery isn't dead.
  2. Isolate and Lock Off: Turn off the MCB/RCBO for the circuit at the consumer unit. Apply a physical lockout/tagout device if you are in a shared or commercial environment.
  3. Verify Dead: Test between Line and Neutral, Line and Earth, and Neutral and Earth at the point of work. The meter must read 0V (or < 2V induced ghost voltage) on all combinations.
  4. Re-prove your meter: Test the meter on the known live source again to ensure it didn't fail during the dead test.
  5. Execute Continuity Testing: With the circuit confirmed dead, use the decision tree above to map the conductors via continuity to the distribution board buses.
  6. Sleeve and Label: Once identified, permanently alter the wire's visual identity using 600V-rated heat shrink or high-quality PVC tape (e.g., 3M Temflex or Super 33+). Update the circuit schedule on the consumer unit door to reflect the non-standard colours.
Never use a non-contact voltage tester (NCVT) or 'volt stick' as your primary proof of dead. NCVTs detect capacitive coupling and can yield false negatives on shielded cables or false positives from adjacent live circuits. Always use a calibrated two-pole voltage indicator or a CAT III/IV digital multimeter for final verification.