Electrical wiring colour codes

Electrical engineers and electricians follow predefined wiring colour codes while wiring houses, commercial buildings and industrial panel boards. The colour codes followed is slightly different in every part of the world depending on the standards they follow. Even there are different colour codes for AC and DC wires. For example, in Canada, you can find Red, black and blue wires for three-phase, whereas, in Australia, it is Yellow, blue and black. In this article, let us discuss wiring codes followed in different countries.

IEC Standard wiring colour codes

The international standard, IEC 60446 (International Electro-technical Commission, an organization that prepares and publishes electrical and electronics technologies) defines the colour codes as below:

For a three-phase AC system,

The preferred colour codes shall be:

Phase – 1: Brown
Phase – 2: Black
Phase – 3: Grey
Neutral: Light blue
Earth or protective conductor: Green/Yellow

For a Single-phase AC system,

Phase: Brown
Neutral: Light blue
Earth or protective conductor: Green/Yellow

Wiring color code followed in European Union and UK

For a 2-Wire Unearthed DC system:

Positive: Brown
Negative: Grey

For a 2-Wire Earthed (of a Negative Earthed) DC Circuit system:

Positive: Brown
Negative: Blue

For a 2-Wire Earthed (of a Positive Grounded) DC Circuit system:

Positive: Blue
Negative: Grey

3-Wire Earthed DC:

Positive: Brown
Mid-Wire: Blue
Negative: Grey

Protective Earth: Green-Yellow

The above-mentioned colour codes are followed in the European Union, United Kingdom, China, Hong Kong, Argentina, Russia, Ukraine, Belarus, Kazakhstan and Singapore.

NEC Standard wiring colour codes

National Electrical Code is followed in the United States and sometimes in Canada. NEC mandates the colour codes for neutral and protective ground as grey and yellow-green respectively. NEC does not instruct any requirements for other conductors. The colour code adopted in the US is as follows:

The preferred colour codes shall be:

Phase – 1: Black (for 120, 208, or 240 V), Brown (for 277, or 480 V).
Phase – 2: Red (for 120, 208, or 240 V), Orange (for 277, or 480 V).
Phase – 3: Blue (for 120, 208, or 240 V), Yellow (for 277, or 480 V).
Neutral: White (for 120, 208, or 240 V), or Grey (for 277, or 480 V)
Earth or protective conductor: Green/Yellow or Green or bare copper conductor.
For single-phase, Black (for 120V) or Red (for 277) is used for Line and Grey is used for Neutral.

Wiring color code followed in the US and Canada

Australian Standard / New Zealand standard for wiring colour codes

AS/NZS prohibits the usage of yellow, green, yellow-green, black and sky blue colours for phases. Any colours other the listed can be used. The commonly used colour code is as follows:

For a three-phase supply – Red, white and blue colours are used.
For a single-phase supply – Red or brown is used for line and black or sky blue is used for neutral.
For Earth or protective conductor – Green/Yellow or Green or bare copper conductor can be used.