Cable colour codes

These colour codes are offered as guidance in allocating circuits and investigating existing installations. Many installers abbreviate colours to their initial and last letters – Bk for Black, Bn for Brown. An alternative is to use the initial letter, but to avoid duplication, under this system Black is K, Brown is N and Grey is S (for Slate). BBC designed cables usually use Slate instead of Grey, but as the two colours are very similar, and are never both used in the same cable, they are effectively interchangeable. The BBC colour codes are explained in ED122 Guide to Wiring (stock code 0446493).

Where two colours are shown separated by a hyphen, the first colour is the primary colour, usually the base colour, with the second (and third where appropriate) applied as thin bands or stripes. Occasionally cables are manufactured with less of the primary colour showing than the secondary colour (sometimes within the same cable) but this should not lead to confusion. In the CW1308 standard the primary/secondary colours are rigidly defined, and the primary colour (shown in capitals) is always the base colour.

Multipair cables have repeated solid colours as primaries, and the pair number is identified by the colour of the other half of the twisted pair – care should be taken when preparing these cables to ensure the correct pairing is maintained.