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UK Wiring Colour Codes — Old vs New
Complete reference for UK electrical wiring colour changes introduced in 2004 (harmonised colours) and fully enforced from 2006. Critical for identifying existing installations.
Single-Phase Wiring Colours
| Conductor | Old Colour (pre-2006) | New Colour (post-2004) |
|---|---|---|
| Live (Line) | Red | Brown |
| Neutral | Black | Blue |
| Earth (CPC) | Green/Yellow | Green/Yellow |
Three-Phase Wiring Colours
| Conductor | Old Colour (pre-2006) | New Colour (post-2004) |
|---|---|---|
| Line 1 (L1) | Red | Brown |
| Line 2 (L2) | Yellow | Black |
| Line 3 (L3) | Blue | Grey |
| Neutral | Black | Blue |
| Earth (CPC) | Green/Yellow | Green/Yellow |
Critical Safety Warning
Note that black changed from neutral (old system) to Line 2 (new system), and blue changed from Line 3 (old system) to neutral (new system). Misidentifying these conductors can be fatal. Always test with a voltage indicator before working on any circuit. Old colours may still be present in existing installations and must be identified correctly before any extension or alteration work.
Switch Wires and Two-Way Switching
| Function | Old Colour | New Colour | Notes |
|---|---|---|---|
| Permanent live to switch | Red | Brown | — |
| Switched live (return) | Black (with red sleeve) | Blue (with brown sleeve) | Sleeved to indicate it is a switched live |
| Two-way strapper 1 | Yellow | Black | In three-core and earth cable |
| Two-way strapper 2 | Blue | Grey | In three-core and earth cable |
Warning Notice Requirements
BS 7671 Regulation 514.14 requires a warning notice at every distribution board, consumer unit, or junction box where conductors of both old and new colours are present. The notice must read:
"Caution — This installation has wiring colours to two versions of BS 7671. Great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified."
Standards Reference
The colour change was introduced by BS 7671:2001 Amendment No. 2:2004, which adopted the harmonised cable colours from HD 308 S2 (now EN 60446). The current edition is BS 7671:2018 + Amendment 2:2022 (the IET Wiring Regulations, 18th Edition). Always refer to the current edition for definitive requirements.
Related Pages
See the BS 7671 Domestic Circuit Guide for cable sizes and MCB ratings, the UK Cable Sizes reference, and the BS 7671 18th Edition Changes summary.
Next up: related pages
Frequently Asked Questions
The UK harmonised with European wiring colours on 31 March 2004 (BS 7671:2001 Amendment 2). A transition period ran until 31 March 2006 during which either set of colours was permitted. After 1 April 2006, all new installations must use the new harmonised colours. However, existing installations with old colours remain legal and do not need to be rewired solely because of the colour change.
If old and new colours exist in the same installation, a warning notice must be fitted at the consumer unit or distribution board stating: "Caution — This installation has wiring colours to two versions of BS 7671. Great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified." This is a requirement of BS 7671 Regulation 514.14.
Yes, old wiring colours are perfectly safe provided the installation is in good condition and has a valid Electrical Installation Condition Report (EICR). The colour change was for harmonisation with European standards, not for safety reasons. The key danger is misidentification when old and new colours are mixed in the same circuit, which is why warning notices are required.
The earth conductor (circuit protective conductor, CPC) colour did not change — it remains green/yellow striped in both old and new systems. Bare earth conductors in twin-and-earth cable must be sleeved with green/yellow sleeving at every termination point.
Old three-phase colours were red (L1), yellow (L2), blue (L3) with a black neutral. New harmonised colours are brown (L1), black (L2), grey (L3) with a blue neutral. Note that black changed from neutral (old) to Line 2 (new) and blue changed from Line 3 (old) to neutral (new) — a particularly dangerous source of confusion if both systems are present.
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Last updated: April 2026
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