Beginner6 min readUpdated 2024

Cable Colour Codes — All Regions

Side-by-side conductor colours for the UK, Europe, North America and Australia/New Zealand — plus the old codes you'll still meet.

BS 7671 / IEC 60446CENELEC HD 308 S2NEC (NFPA 70)AS/NZS 3000

Colour tells you a conductor's function, not that it is safe — always prove dead. This is a working reference for the harmonised European colours, the North American convention, the Australian/New Zealand scheme, and the pre-harmonised colours you'll find in older installations.

UK & Europe (harmonised, post-2004)

Since the harmonisation of BS 7671 with CENELEC HD 308 S2, the UK uses the same fixed-wiring colours as the rest of Europe. Green-and-yellow is reserved exclusively for the protective (earth) conductor — never use it for anything else.

Brown

Line (single phase)

Blue

Neutral

Green / Yellow

Protective earth

Brown

Line 1 (3-phase)

Black

Line 2 (3-phase)

Grey

Line 3 (3-phase)

Switch drops & sleeving

A blue conductor used as a switched line (a 'switch wire') must be over-sleeved brown at both ends. The same applies to black/grey used as lines. Blue is only a neutral when it is actually working as one.

Old UK colours (pre-2006 installations)

You will meet these for years to come. The dangerous overlap: old red was line, but new blue neutral and old black neutral can be confused, and old green earth (pre-1970) is not the same as modern green-and-yellow. When you extend an old installation, a warning notice about mixed colours is required at the consumer unit.

Function	Old UK	Harmonised (now)
Line / phase 1	Red	Brown
Phase 2	Yellow	Black
Phase 3	Blue	Grey
Neutral	Black	Blue
Earth	Green (or green/yellow)	Green / Yellow

The classic trap

Old blue was a phase; new blue is neutral. Old black was neutral; new black is a phase. Never assume — prove dead and confirm function before terminating.

North America (NEC / NFPA 70)

The NEC fixes neutral (white or grey) and ground (green, green/yellow or bare) but leaves ungrounded 'hot' colours largely to convention, which differs by system voltage. The common practice is:

System	Hot conductors	Neutral	Ground
120/240 V single phase	Black, Red	White	Green / bare
120/208 V three phase (Y)	Black, Red, Blue	White	Green
277/480 V three phase (Y)	Brown, Orange, Yellow	Grey	Green

Colours above 277/480 V follow local/plant convention; the neutral and ground rules are the fixed requirements.

Australia & New Zealand (AS/NZS 3000)

Function	Current colours	Older colours you may find
Active (line)	Brown (or any except those below)	Red
Neutral	Blue	Black
Earth	Green / Yellow	Green
3-phase actives	Brown, Black, Grey	Red, White, Blue

One rule everywhere

Green/yellow (and green) is always earth. If you see it doing anything else, stop and investigate — someone has mis-wired the installation.

Reference material for qualified electrical work. Figures follow BS 7671 and the IET On-Site Guide unless stated; always confirm against the current edition and the standard that applies to your installation.

UK & Europe (harmonised, post-2004)

Old UK colours (pre-2006 installations)

North America (NEC / NFPA 70)

Australia & New Zealand (AS/NZS 3000)

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