A standard UK plug has three wires. What color is the neutral wire? What color is the live wire? What color is the earth wire?
If we were to take such a plug, turn it around, and remove the back, we would see these three wires. There is one which is green and yellow, one which is a blue color, and one which is brown. These three colors correspond to the live wire, the earth wire, and the neutral wire. We can say then that the neutral wire is blue, the live wire is brown, and the earth wire is green and yellow.