What Colour Is the Live Wire?

In a modern UK home, the live wire is brown. The neutral wire is blue, and the earth wire is green and yellow. Electrical Safety First uses those colours in its plug guidance, and notes that older plugs used a different set, just as older house wiring does.

For homeowners doing their own electrics, that sounds simple, but we would always add an important warning: colour alone is not enough to identify a conductor safely. Older homes can contain older colour schemes, mixed-age alterations, or previous work that does not match modern expectations, which is why testing matters more than the colour of the insulation.

Modern UK wire colours

The answer most people are looking for is straightforward: brown is live in modern UK domestic wiring. Blue is neutral and green/yellow is earth. That is the current colour system homeowners are most likely to see in newer installations, replacement accessories, and recently updated circuits.

That also means that if a homeowner opens an accessory and sees brown, blue, and green/yellow, they are looking at the current UK colour convention. But that still does not make the circuit safe to work on without proper isolation, testing, and competence. HSE's position is that you can do your own electrical work only if you are competent to do it.

UK wire colour chart: old and new

The UK changed to the harmonised European colours with a 2004 amendment to BS 7671. There was a changeover period when either set could be used, and new fixed wiring has used only the new colours since 2006. So a house wired or altered before then can have either, or both. Old colours are not a fault in themselves: Approved Document P says adequate existing cables do not need replacing just because they use the old colour codes.

• Live (line), single phase: brown now, red before 2004.

• Neutral: blue now, black before 2004.

• Earth (protective conductor): green/yellow now. Appliance flex made before about 1970 used plain green. In fixed twin and earth cable the earth is a bare copper core, which should have green/yellow sleeving where it enters an accessory (older installs may have plain green sleeving, or none).

• Three-phase lines (L1, L2, L3): brown, black and grey now; red, yellow and blue before 2004.

• 3 core and earth cable (two way switching): brown, black and grey now; red, yellow and blue before 2004.

Flexible cords on appliances switched to brown, blue and green/yellow in 1969, more than 30 years before fixed wiring did, which is why plugs have used the modern colours for so long. Our guide on how to wire a plug covers flex colours and terminals.

Older house wiring can be different

In older UK installations, the live wire may be red rather than brown, and the neutral may be black rather than blue. Electrical Safety First's plug guidance gives the same old colours for older plugs: red for live, black for neutral and green for earth.

This is where many DIY jobs become risky. A house may have had partial updates over time, so one area may use newer colours while another still uses older wiring. That is especially common in properties that have had extensions, kitchen refits, fuse board changes, or partial rewiring at different points in their history. Where new work in the new colours is added to an installation wired in the old ones, BS 7671 requires a caution notice on or near the consumer unit saying both colour systems are present.

When black is live: the trap in modern wiring

If you learnt "black is neutral" from old wiring, modern cable can catch you out. In brown, black and grey 3 core cable, black is a line conductor, not a neutral. You will find it in two way lighting circuits and in three-phase supplies, where black is the second line (L2) and can carry 400 volts relative to the other lines.

The same goes for blue in a lighting switch cable. In the twin and earth cable that drops from a ceiling rose to a switch, the blue core carries the switched live back to the light. It should be sleeved brown at both ends, but often is not. Our guide to wiring a two way light switch shows where these cores go. The rule is simple: any core can be live, whatever its colour, until it has been proved dead.

Why colour alone is not enough

The biggest mistake a homeowner can make is assuming that the wire colour tells the whole story. Even if the colours look familiar, that does not confirm the circuit has been isolated correctly, terminated correctly, or left in a safe condition by previous work. That is why Approved Document P says all electrical installation work in a home, notifiable or not, should be inspected, tested and certificated to BS 7671.

That is why, at SM Electrical, we recommend a qualified electrician rather than DIY fault-finding or guesswork. We are registered with a Competent Person Scheme, fully qualified, and we carry out work to BS 7671, with certification where required.

If the colours do not match what you expect

Stop and do not guess. Colours that do not line up with either the old or new system usually mean an earlier alteration, a borrowed neutral, or a DIY repair. Signs worth acting on:

• red and black in one room, brown and blue in the next, with no warning notice at the consumer unit

• a blue or black core connected where the live should be, with no brown sleeving

• earth cores with no sleeving, or no earth at all at light fittings

• rubber or fabric-covered cable, which predates modern PVC cable and is well past its expected life

Any of these is a reason to have the installation tested before more work is done on it.

When a homeowner should call a professional

If the question is simply "what colour is the live wire?", the answer is brown in modern UK wiring. But if the real situation is that a homeowner has opened up a socket, light fitting, switch, or junction point and is trying to work out what is what, that is usually the point where we would advise calling a professional.

We would particularly recommend professional help where there are signs of age or electrical problems, such as tripping circuits, burning smells, buzzing sockets, outdated fuse boards, damaged accessories, or uncertainty about the age of the wiring. Older consumer units may not meet current safety rules or provide modern RCD protection.

A safer next step than DIY guesswork

For many homeowners, the safest next step is not to keep tracing colours by eye but to arrange a proper inspection. An EICR report checks the consumer unit, sockets, switches and wiring, including how conductors are identified and whether the right notices are in place, and flags risks or outdated circuits with a code.

That is often the right route if a property is older, if the electrics have not been inspected in years, or if there is any doubt about previous alterations. If the report shows the old wiring has reached the end of its life, rewiring all or part of the house brings every circuit onto the modern colours. We are based in Shifnal and work across Wolverhampton, Telford, Shropshire and the wider West Midlands, with testing and certification at the centre of every job.