Wire colour codes in the UK changed some years ago to come in line with EU standards
The wiring from your fuse box for all you household circuits is hidden behind walls ceiling voids etc. This cable is called "twin and earth" cable.
Underneath an outer insulation you have a live, neutral and earth cable. Unlike the live and neutral the earth does not have it's own separate insulation. When terminated at lights sockets etc. earth sleeving must be put on any bare wire.(green and yellow stripey)
If you have old electrical wiring
your colours will be different from current colours. There may be times when you need to know what colour is live.
Some years ago the colours on the live and neutral changed from red(live) and black(neutral) to come in line with the colours that have been used for many years on appliances like kettles, toasters etc. These are Brown(live) Blue(neutral)
So, for OLD electrical wiring red live black neutral.
For NEW electrical wiring brown live blue neutral