From 1st April 2004 the colours for the conductor insulation for new installations for electrical wiring and house wiring changes to the colours shown in BS7671 table 51. You must take great care when installing and connecting the cables where old and new Cale colours are present in the same building.
You can find the new wiring and cable insulation colour code in the On-Site Guide BS7671:2018. Appendix K table K1 – Identification of conductors (Harmonised)
See below table –
| Function | Alphanumeric | Colour |
| Protective conductors | Green and Yellow | |
| Functional earthing conductor | Cream | |
| AC Power Circuit | ||
| Line of single-phase circuit | L | Brown |
| Neutral of single- or three-phase circuit | N | Blue |
| Line 1 of three-phase AC circuit | L1 | Brown |
| Line 2 of three-phase AC circuit | L2 | Black |
| Line 3 of three-phase AC circuit | L3 | Grey |
| Two-wire unearthed DC power circuit | ||
| Positive of two-wire circuit | L+ | Brown |
| Negative of two-wire circuit | L- | Grey |
| Two-wire earthed DC power circuit | ||
| Positive (of negative earthed) circuit | L+ | Brown |
| Negative (of negative earthed circuit² | M | Blue |
| Positive (of positive earthed circuit² | M | Blue |
| Negative (of positive earthed circuit | L- | Grey |
| Three-wire DC power circuit | ||
| Outer positive of two-wire circuit derived from three-wire system | L+ | Brown |
| Outer negative of two-wire circuit derived from three-wire system | L- | Grey |
| Positive of three-wire circuit | L+ | Brown |
| Mid-wire of three-wire circuit²,³ | M | Blue |
| Negative of three-wire circuit | L- | Grey |
| Control circuits, ELV and other applications | ||
| Line conductor | L | Brown, Black, Red, range, Yellow, Violet, Grey, White, Pink or Turquoise |
| Neutral or mid-wire4 | N or M | Blue |
Notes:
- Power circuits include lighting circuits.
- M identifies either the mid-wire of a three-wire DC circuit, or the earthed conductor of a two-wire earthed DC circuit.
- Only the middle wire of three-wire circuits may be earthed.
- An earthed PELV conductor is blue.
What are the old installation wiring colours compared to the new wiring colours?
Single Phase Installations
| Conductor | Old Colour | New Colour |
| Phase | Red | Brown |
| Neutral | Black | Blue |
| Protective Conductor | Green and Yellow | Green and Yellow |
Three Phase Installations
| Phase of a.c | Old Colour | New Colour |
| Phase one | Red | Brown |
| Phase two | Yellow | Black |
| Phase three | Blue | Grey |
| Neutral | Black | Blue |
| Protective Conductor | Green and Yellow | Green and Yellow |