Cable colour codes for wiring in the UK changed in April 2006. They are now the same colours as those used in flex which was last changed back in the 1960s.
When the cable is stripped for connecting to an accessory, the bare earth conductor should be covered with green and yellow PVC sleeving
Three core and earth
In three core & earth cable, there is an additional core. The old colours for this cable, commonly used for two way lighting, were red, yellow, and blue. The new colours are brown, black, and grey.
In three core & earth, any or all of the cores may be live. The colours are used for identification only.