UK wiring colours: old and new explained
By Azzeddine Kebbi, NAPIT-registered electrician and director of Kebbi Electrical Services · Updated 10 November 2026
UK wiring colours changed in 2004. Here is what each colour means in old and new installations, how to tell which you have, and when old wiring needs checking.
First, stay safe
- Always switch off and isolate at the consumer unit before looking at any wiring, and never touch bare conductors.
- Colours tell you what a wire is meant to be, not that it is safe or dead. Only a test proves a circuit is off.
- If you are not sure, leave it and call a registered electrician.
New colours (since 2004)
| Wire | Colour |
|---|---|
| Live (line) | Brown |
| Neutral | Blue |
| Earth | Green and yellow |
These are the harmonised colours used across Europe. Every new circuit, rewire and alteration in the UK must use them.
Old colours (before 2004)
| Wire | Colour |
|---|---|
| Live (line) | Red |
| Neutral | Black |
| Earth | Green and yellow (plain green in very old installations) |
If you lift a socket or light fitting in a home wired before 2004, you will usually see red and black. Many homes in Bristol still have them.
Three-phase colours
| Wire | Old | New |
|---|---|---|
| Line 1 | Red | Brown |
| Line 2 | Yellow | Black |
| Line 3 | Blue | Grey |
| Neutral | Black | Blue |
| Earth | Green and yellow | Green and yellow |
Three-phase supplies are mostly found in commercial buildings. Note that black and blue swap meaning between old and new, which is why mixed installations need clear labelling.
What the colours tell you about your wiring
Red and black
Wired or rewired before 2004. Not unsafe on its own, but the installation may be 20+ years old.
Plain green earth
Usually a very old installation. Worth having it inspected.
Black rubber or fabric-covered cable
Often 1960s or earlier. This insulation can perish, so have it inspected soon.
Mixed old and new
Alterations made after 2004. There should be a warning notice at the consumer unit.
The way to know your wiring is safe is an Electrical Installation Condition Report. See EICR in Bristol and EICR codes explained.
Common questions
Working out a switch? See light switch wiring explained.
When did UK wiring colours change?
New installations have used brown (live) and blue (neutral) since 31 March 2004. From then until 31 March 2006 either set of colours was allowed, and from April 2006 all new work must use the new colours.
Is old red and black wiring dangerous?
Not because of the colours. Plenty of red and black wiring is still in good condition. What matters is the cable's age and condition, which an EICR checks.
What does a green-only earth wire mean?
A plain green earth usually means a very old installation. It is worth having an EICR to check the condition of the wiring.
Do I need a notice if my home has both old and new colours?
Yes. Where old and new colours are mixed, a warning notice should be fixed at or near the consumer unit so anyone working on it knows. We fit one when we extend or alter older wiring.
Worried about old wiring?
We inspect and test older installations across Bristol and tell you plainly what needs doing, from a simple EICR to a partial or full rewire.