Do you know that, as of April next year, the mains wiring colours will change for the UK? In fact, any electrical work now should use the new colours already, but you're still allowed to use the old ones if you've got left-over bits of cable for now.
Current colours: Red, Yellow and Blue denote the 3 phases, Black denotes neutral, and Green (sometimes with yellow stripes) denotes earth. And this is all very well and makes pefect sense as long as you're not colour-blind. If you are, then electrician is one of those jobs which is not for you.
Until the EU got their way, at which point they decided to change all the colours. Oh, and you don't refer to the phases by colour anymore - you label them "L1", "L2" and "L3" instead. So the new colours are Brown, Black and Grey for the phases, Blue for neutral, and Green with Yellow stripes for the earth.
Have you worked out the fun part yet? This table might help: