Old wiring colours UK (and the new ones)
Every old wiring colour UK installs used before 2006, side by side with the harmonised colours that replaced them. Plus the straight answer on whether red and black means a rewire (spoiler: usually not).
UK wiring colours: old vs new
Single-phase (domestic fixed wiring)
| Conductor | Old colour (pre-2006) | New colour (2006 on) |
|---|---|---|
| Live (line) | Red | Brown |
| Neutral | Black | Blue |
| Earth (CPC) | Green/Yellow (bare or solid green on very old installs) | Green/Yellow |
Three-phase
| Conductor | Old colour | New colour |
|---|---|---|
| Line 1 | Red | Brown |
| Line 2 | Yellow | Black |
| Line 3 | Blue | Grey |
| Neutral | Black | Blue |
Danger, read this twice. On three-phase, old blue was a phase, but new blue is neutral. And old black was neutral, but new black is a phase. That crossover is exactly how people get hurt. Always test, never trust colour alone.
Flexes and appliance cords
| Conductor | Old flex colour | New flex colour (early 1970s on) |
|---|---|---|
| Live (line) | Red | Brown |
| Neutral | Black | Blue |
| Earth | Green (solid) | Green/Yellow |
Flexes swapped over decades before fixed wiring did, which catches people out. Strip back a cord and find red, black and solid green? That appliance has been going since before decimal currency. The flex is life-expired, replace it, or better, retire the whole thing.
Old electrical wiring colours, explained properly
Here's the timeline in one breath. The harmonised European colours were introduced to BS 7671 in 2004, and from 31 March 2006 they became mandatory for all new fixed wiring. That's the day red and black officially became "old colours". Flexible cords jumped ship decades earlier, brown and blue arrived on flexes in the early 1970s, which is why your nan's table lamp was ahead of her house wiring by about thirty years.
Why the earth went stripy is worth knowing too. The old solid green earth was replaced by green/yellow partly because solid colours are a genuine problem for anyone with red/green colour blindness. The stripes are unmistakable to everyone, which is exactly what you want from the one conductor that exists purely to save lives.
What each wire actually does
Quick primer for the homeowners in the room, electricians can skip ahead. The live (line) conductor carries power out to your sockets, lights and appliances at 230 V. The neutral completes the circuit and carries the current back. The earth (the CPC, if you want the trade term) does nothing at all in normal service, then when a fault occurs it carries the fault current away so the fuse, MCB or RCD can cut the power fast. Which is why a sound earth matters more than any colour on this page.
Is red and black wiring illegal?
No, and I'll say it louder for the people at the back: red and black wiring is not illegal and does not automatically need rewiring. There was never a law forcing anyone to rip out perfectly good cable just because the colour scheme changed. Age and condition decide whether an installation needs work, not the shade of the insulation. Millions of UK homes still run happily on red and black.
On an EICR, old colours by themselves are typically no code at all, or a C3 at most, "improvement recommended", provided the conductors can be clearly identified. If a report lands in front of you (or your customer) full of codes and jargon, my EICR codes explained page decodes what C1, C2, C3 and FI actually mean for the wallet.
Mixing old and new colours in one installation
Extend a red and black circuit with brown and blue cable and you've got two colour systems living under one roof. That's fine, BS 7671 allows it, but it requires a warning notice at the consumer unit reading: "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." It costs pennies and takes ten seconds to fit, so there's no excuse for a board without one.
How to date wiring from its colours
Colours won't tell you the condition of an installation, but they make a decent carbon-dating kit for its age:
| What you can see | Rough era | What it tells you |
|---|---|---|
| Brown and blue fixed wiring | 2006 onwards | Wired or rewired under the harmonised colours |
| Red and black, green/yellow earth sleeving | Roughly 1977 to 2006 | Pre-harmonisation but usually PVC throughout, condition decides everything |
| Red and black, solid green earth sleeving | Pre-1977 | Vintage territory, inspect carefully for rubber insulation |
| Flex with red, black or solid green cores | Pre-early 1970s | The cord is over fifty years old, replace it |
One caveat: colours date the most recent work on the circuits you can see, not the whole house. Plenty of "brown and blue" homes still have red and black lurking on untouched circuits upstairs. Test everything, assume nothing.
When old colours ARE a rewire conversation
Colour isn't the problem, but it's sometimes a clue to the real problem: age. On very old installs, pre-1977 earth sleeving could be solid green rather than green/yellow, which tells you you're deep in vintage territory. And if you open things up and find rubber-insulated (VIR) or lead-sheathed cable from the 1950s and 60s, that IS a genuine rewire conversation. The rubber insulation dries out and crumbles the moment you disturb it, and no amount of sleeving fixes that.
Other red flags that put a rewire on the table, whatever colour the conductors are:
- Rubber (VIR), fabric-braided or lead-sheathed cable anywhere. Find it at the board and you'll almost always find more of it buried in the walls.
- Round-pin sockets, a wooden-backed fuse board or rewirable fuses, all signs the installation predates modern protection by decades.
- No earth conductor on the lighting circuits, common in homes wired before the mid-1960s, and a real limitation on which fittings can safely be installed.
- Insulation that cracks or crumbles when a conductor is moved. That's the cable telling you it's finished, believe it.
Buying or selling a house with old colours
Buying? Red and black on its own shouldn't scare you off, but it does tell you the wiring is at least twenty years old, possibly far more. A mortgage survey will usually just note "older electrical installation, testing recommended" and move on, which tells you precisely nothing. Commission an EICR before exchange. It's a small spend against the price of a house, and if it comes back with C1s and C2s you're holding a genuine negotiating lever, because now the rewire has a price and it's on the table.
Selling? There's no law forcing you to rewire before selling, and old colours won't block a sale. A recent satisfactory EICR is the cheapest way to take the electrics off the table before a buyer's surveyor puts them on it. Landlords in England don't get a choice, a satisfactory EICR at least every five years is a legal requirement for rented property.
Practical rules I'd tattoo on every apprentice
- Always prove dead before you touch anything. Colours lie, especially after forty years of DIY interference by previous owners with more confidence than sense.
- Extending an old circuit? Sleeve and label so the next person (probably future you) can identify every conductor at a glance.
- Find a black conductor used as a switched live with no sleeving? Sort it while you're in there. Two minutes of sleeving now saves someone a very bad day later.
While you're crawling around an older property, two of my other references usually earn their keep: the bathroom electrical zones guide for what's allowed where around the tub, and the IP rating checker for decoding what those IP numbers on a fitting actually promise.
Wiring colours FAQs
When did wiring colours change in the UK?
The harmonised European colours were introduced to BS 7671 in 2004, with a transition period where both systems were acceptable. From 31 March 2006 the new colours became mandatory for all new fixed wiring. Flexible cords made the change decades earlier, brown and blue turned up on appliance flexes in the early 1970s.
Do red and black wires mean I need a rewire?
No. Red and black is simply the pre-2006 colour scheme, it's not illegal and there's no requirement to replace it. What matters is the age and condition of the installation, and the honest way to judge that is an EICR, not a glance at the colours. Plenty of red and black installs are in better nick than botched modern ones.
What colour is the live wire in the UK?
Brown, under the current standard. Before 2006 it was red. On three-phase the lines are now brown, black and grey, where they used to be red, yellow and blue. And whatever the colour claims, test before you touch, conductors don't always match the label after years of alterations.
Can old and new colours be mixed in one installation?
Yes, and it happens every time an old circuit gets extended with new cable. BS 7671 requires a warning notice at the consumer unit stating the installation has wiring colours to two versions of BS 7671, so that anyone working on it takes care identifying conductors. Mixed colours with the notice fitted is completely acceptable.
What do red, yellow and blue wires mean?
Those are the old three-phase line colours. Under the current standard the three lines are brown, black and grey. The trap: old blue was a phase but new blue is neutral, and old black was neutral but new black is a phase. On any three-phase job with mixed-era wiring, test every conductor and trust nothing.
Is a house with old wiring colours safe to buy?
Usually, yes. Old colours just tell you the fixed wiring predates 2006, they say nothing about its condition. My advice for buyers: budget for an EICR as part of the purchase, it's a small cost that tells you whether you're inheriting a sound installation or a bill. If the survey mentions rubber or lead-sheathed cable, budget properly.
What were the old colours on appliance flexes?
Red for live, black for neutral and plain green for earth. Flexes harmonised decades before fixed wiring, brown, blue and green/yellow appeared on appliance cords in the early 1970s. So if you find a flex with red and black cores today, that cord is over fifty years old. Replace it, or better, retire the appliance.
How can I tell how old my wiring is from the colours?
Rough guide: brown and blue means 2006 or later. Red and black with green/yellow earth sleeving puts it somewhere between 1977 and 2006. Red and black with solid green sleeving is pre-1977, proper vintage. Colours only date the circuits you can see though, an EICR is the honest way to judge the whole installation.
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