Cables in domestic premises are to change from red and black to brown (phase) and blue (neutral) respectively.
The changes have been confirmed by the National Committee for Electrical Installations and will be published in Amendment No 2 to BS 7671: 2001, the IEE Wiring Regulations, on 31 March 2004. The amendment will also introduce a new appendix providing guidance on how to connect the new coloured cables to existing installations that are wired in the old colours.

There will be a two-year overlap period, during which cables in the old or new colours can be used but they can not be installed together. After 31 March 2006 only installations using the new colours will conform to BS 7671.

The British Electrotechnical Committee has set up a special group, L/12, to bring the changes to the attention of the public and professional trades.

The change will align the electrical installation wiring colours with those of flexible cables of appliances and equipment.

Source

Electrical and Mechanical Contractor