International standard IEC 60446 defines basic safety principles for identifying electrical conductors by colours or numerals, for example in electricity distribution wiring.

Permitted colours

The standard permits the following colours for identifying conductors:

black

Black

Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light...

, brown

Brown

Brown is a color term, denoting a range of composite colors produced by a mixture of orange, red, rose, or yellow with black or gray. The term is from Old English brún, in origin for any dusky or dark shade of color....

, red

Red

Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...

, orange

Orange (colour)

The colour orange occurs between red and yellow in the visible spectrum at a wavelength of about 585–620 nm, and has a hue of 30° in HSV colour space. It is numerically halfway between red and yellow in a gamma-compressed RGB colour space, the expression of which is the RGB colour wheel. The...

, yellow

Yellow

Yellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...

, green

Green

Green is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...

, blue

Blue

Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...

, violet

Violet (color)

As the name of a color, violet is synonymous with a bluish purple, when the word "purple" is used in the common English language sense of any color between blue and red, not including either blue or red...

, grey

Grey

Grey or gray is an achromatic or neutral color.Complementary colors are defined to mix to grey, either additively or subtractively, and many color models place complements opposite each other in a color wheel. To produce grey in RGB displays, the R, G, and B primary light sources are combined in...

, white

White

White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.White light can be...

, pink

Pink

Pink is a mixture of red and white. Commonly used for Valentine's Day and Easter, pink is sometimes referred to as "the color of love." The use of the word for the color known today as pink was first recorded in the late 17th century....

, turquoise

Turquoise (color)

Turquoise or is a slightly blueish tone of light green. The color is based on the gem turquoise. The term comes from the French for Turkish.At right is displayed the X11 color named turquoise....

(The colours green and yellow on their own are only permitted where confusion with the colouring of the green/yellow protective conductor is unlikely. Combinations of the above colours are permitted, but green and yellow should not be used in any of these combinations other than as green/yellow for the protective conductor.)

Neutral or mid-point conductor

If a circuit includes a neutral or mid-point conductor, then it should be identified by a blue colour (preferably light blue). Light blue must not be used for any other type of conductor.

AC phase conductors

The preferred colours for AC phase conductors are black, brown and purple

UK Colours to 17th Edition are Brown, Black, Grey, Neutral Blue

Protective conductor

The colour combination green/yellow is always and exclusively used to identify the protective conductor. On any 15 mm length of the conductor, one of these two colours should cover between 30% and 70% of the area and the other the remaining AREA.

PEN conductor

Insulated PEN conductors should be marked either green/yellow along their entire length with light blue markings at their ends, or light blue along their entire length with green/yellow markings at the ends.

United States, Canada and Japan

The three countries United States, Canada and Japan are mentioned in a note in the standard for using different colours:

• white or natural grey for mid-wire or neutral conductor (instead of light blue)
• green for the protective conductor (instead of green-and-yellow)

United Kingdom

British Standard BS 7671

BS 7671

British Standard BS 7671 "Requirements for electrical installations" is the national standard in the United Kingdom for low voltage electrical installations....

:2001 Amendment No 2:2004 adopted the IEC 60446 colours for fixed wiring in the United Kingdom http://www.iee.org/Publish/WireRegs/cablecol.cfm, with the extension that grey can also be used for line conductors, such that three colours are available for three-phase installations. This extension is expected to be adopted across Europe and may even find its way into in a future revision of IEC 60446.

Numbering

Where conductors are in addition identified by numbers, then these numbers must be written in Arabic numerals, digits 6 and 9 must be underlined, and green-and-yellow conductors must not be numbered.