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.
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Last updated: April 2026
All calculations are estimates. Verify with your supplier.