If you’ve opened up a socket, light fitting or consumer unit in a UK home, you may have encountered two completely different colour schemes — and wondered which wire is which. Here’s a straightforward guide to UK electrical wire colours, old and new.
Why are there two different colour systems?
The UK changed its electrical wiring colours in 2004–2006 to align with the rest of Europe. Installations wired before 2004 use the old British colour code; anything wired from 2006 onwards uses the new harmonised colours. Many homes — particularly those that have had partial rewires or extensions — contain both.
Old UK wire colours (pre-2004)
- Live — Red
- Neutral — Black
- Earth — Green/Yellow stripe (or bare copper)
In old three-phase wiring, the colours were red, yellow, and blue for the three live phases, with black for neutral.
New UK wire colours (post-2006)
- Live — Brown
- Neutral — Blue
- Earth — Green/Yellow stripe (unchanged)
In new three-phase wiring, the live phases are brown, black, and grey — which means black is now a live phase colour rather than neutral, the opposite of the old system.
Quick reference: old vs new
| Function | Old colour (pre-2004) | New colour (post-2006) |
|---|---|---|
| Live | Red | Brown |
| Neutral | Black | Blue |
| Earth | Green/Yellow | Green/Yellow |
What about red and black wires — which is live?
In old UK wiring, red is live and black is neutral. This is the opposite of the new system, where brown is live and blue is neutral. The earth (green/yellow) stayed the same across both systems.
This difference matters if you’re working on a property with mixed old and new wiring — for example, where a new extension has been added to an older house. A black wire in old wiring is neutral; a black wire in new three-phase wiring is live. Never assume.
What about lighting circuits?
Lighting circuits follow the same colour conventions, but you may encounter additional colours in switch cables. In older installations, a red or brown wire is often used as a switch wire (the wire that goes up to the switch and back), even though it isn’t connected to the neutral. These are often wrapped with red or brown tape to indicate they’re switch wires rather than permanent live or neutral conductors.
Is old wiring safe?
The change in wire colours was a standardisation exercise, not a safety recall. Old red-and-black wiring isn’t inherently unsafe — what matters is the condition of the wiring and whether it’s protected properly. Wiring degrades over time, and older installations may lack the RCD protection now required on modern circuits.
An EICR (Electrical Installation Condition Report) will assess the condition and safety of your wiring regardless of age or colour scheme.
Mixed old and new wiring — what to look out for
Where old and new wiring exists in the same installation, junction points should be clearly labelled. Current regulations require a warning notice to be fitted at the consumer unit when the installation contains both colour systems. If you don’t see one, that’s worth flagging to an electrician.
When should old wiring be replaced?
The wire colours themselves aren’t the reason to rewire — age, condition and protection are. Signs that old wiring may need attention include rubber or fabric insulation, round-pin sockets, a fuse box with rewireable fuses, or persistent tripping. An EICR will identify whether the installation is still safe and serviceable.
If you’re unsure about wiring in your property, get in touch — we carry out EICRs and full or partial rewires across Bristol and South Gloucestershire.
