Quick reference: UK lighting cable colours

Colour	Function	Replaced (pre-2006)
Brown	Live (line)	Red
Blue	Neutral, or switched live (with brown sleeving)	Black
Green/yellow stripes	Earth (circuit protective conductor)	Green or bare copper
Black	Strapper L1 in 3-core cable (sleeved brown)	n/a
Grey	Strapper L2 in 3-core cable (sleeved brown)	n/a

Note: in modern UK 3-core and earth cable, black and grey are not neutral or another phase. They are identification colours that must be sleeved brown at every termination when carrying line voltage.

The 2006 colour harmonisation

Before 2006, UK domestic lighting wiring used:

• Red for live
• Black for neutral
• Green (or bare copper) for earth

In 2006, the UK harmonised with European IEC 60446 standards, switching to:

• Brown for live
• Blue for neutral
• Green/yellow stripes for earth

BS 7671 requires these colours for all new UK installations from April 2006. Old red/black wiring is still legal where it already exists, but any new work or extensions must use the new colours, and mixed-colour installations must be clearly labelled at the consumer unit.

Twin and earth (6242Y) – for single-switch drops

The most common UK lighting cable is twin and earth, designated 6242Y. It contains:

• One brown conductor (live)
• One blue conductor (neutral, or switched live with brown sleeving)
• One bare copper earth conductor (sleeved green/yellow at terminations)

Twin and earth is used for the cable from the consumer unit to each ceiling rose, and from the ceiling rose down to a 1-way light switch. Standard UK lighting circuits use 1.0 mm² or 1.5 mm² T+E protected by a 6A or 10A MCB.

Three-core and earth (6243Y) – for 2-way and intermediate switches

2-way switching (two switches controlling one light) and intermediate switching (3+ switch positions) need extra conductors between switches, so the cable used is three-core and earth, designated 6243Y. It contains:

• One brown conductor (live/common)
• One black conductor (strapper L1, sleeved brown at terminations)
• One grey conductor (strapper L2, sleeved brown at terminations)
• One bare copper earth conductor (sleeved green/yellow at terminations)

The black and grey conductors are not indications of neutral and another phase – they are simply identification colours for the two strappers in a 2-way circuit. Both run at full line voltage when their respective switch position is closed, which is why both must be sleeved brown at every termination.

Brown sleeving on switched-live conductors

BS 7671 Regulation 514 and Table 51 specifies that any conductor carrying line voltage must be clearly identified as such. In UK lighting circuits this means:

• The blue conductor in twin-and-earth, when used as a switched live (running from a light switch up to the ceiling rose), must be sleeved with brown identification at both ends.
• The black and grey strappers in 3-core-and-earth must be sleeved brown at every termination (at both switch back-boxes, and at any intermediate switch).
• The earth conductor must be sleeved with green/yellow striped insulation at every termination.

Sleeving is done with brown PVC sleeving or, less commonly, brown identification tape. The sleeving must cover the entire length of stripped conductor visible at the terminal.

Older installations: red, black, and bare copper

In a UK house wired before April 2006, you will typically find:

• Red wires carrying live (where new installations use brown)
• Black wires carrying neutral, or switched live with red sleeving
• Bare copper or green earth (no green/yellow stripes)

Pre-2006 3-core cable used red, yellow, and blue conductors. In 2-way switching with old-colour cable, the strappers were typically yellow and blue, with red sleeving applied to indicate switched live.

When you do new work in a house with old wiring, you must comply with current BS 7671: any new section uses brown/blue/green-yellow, and a warning notice must be placed at the consumer unit indicating that the installation contains both old and new colour conductors.

Identifying cables in your house

Before working on any UK lighting circuit, always:

1. Prove dead first. Use a GS38-compliant two-pole voltage tester. Test the tester against a known live source, then test the circuit, then re-test on the known live source to confirm the tester is still working (the “prove – test – prove” sequence).
2. Note the colour and sleeving of every conductor before disconnecting anything. Old wiring with no sleeving is a hazard – assume blue or black at switch positions is switched live, not neutral.
3. Trace the cable if there is any uncertainty about its function. Use a circuit tracer or switch off MCBs one at a time and confirm the affected circuit.

If you find a UK lighting circuit with unsleeved blue conductors at a switch position, that is standard – the blue is the switched live, and it should have had brown sleeving applied at the time of installation. Add brown sleeving now while you have the cable exposed.

Why the colours matter – BS 7671 18th Edition compliance

Correct cable colour use isn’t cosmetic. Mis-identification of conductors at a UK switch position is one of the most common causes of electric shock and circuit damage during DIY work. The BS 7671 18th Edition is the current UK wiring regulations standard, and proper conductor identification is mandatory for:

• Personal safety during isolation and testing
• Insurance claims after electrical incidents
• Building Control sign-off for notifiable work (Part P)
• EICR (Electrical Installation Condition Report) inspections

Frequently asked questions

Can I mix new (brown/blue) and old (red/black) colours in the same circuit?

Only with a clearly visible warning notice at the consumer unit stating that the installation contains both old and new colour conductors. Best practice when extending old wiring is to replace the existing run rather than splice old colours to new.

Why is the blue wire at my light switch always switched live, not neutral?

Most UK lighting circuits use the loop-in topology, where the neutral runs directly from the rose to the lamp and never reaches the switch. The cable down to the switch contains only live (brown) and switched live (blue, sleeved brown). The blue is acting as the switched return, not as a neutral.

I don’t see brown sleeving on the blue at my switch – is that dangerous?

It is not immediately dangerous if you correctly identify the conductor function (the blue in a switch drop is always switched live in a loop-in installation), but it is non-compliant with BS 7671. Anyone subsequently working on the circuit needs to know the blue carries live voltage when the switch is on. Add brown sleeving the next time you have the cable exposed.

What size cable should I use for UK lighting circuits?

Most domestic UK lighting uses 1.0 mm² or 1.5 mm² twin-and-earth with a 6A or 10A MCB. 1.5 mm² gives more headroom for long cable runs and high-wattage incandescent installations (now rare), while 1.0 mm² is the standard for modern LED-only circuits.

What about the green/yellow stripe orientation – does it matter?

No. The colour pattern itself (alternating green and yellow stripes) is the international code for earth/protective conductor and is recognised regardless of which end is which.