Mains electricity: The insulation covering each wire is colour coded for easy identification:

The idea

Mains cables contain copper conductors surrounded by flexible plastic insulation. That insulation is coloured so that anyone working on a plug, socket or appliance can identify each wire quickly and safely. In a three-core cable, the live wire is brown, the neutral wire is blue, and the earth wire is green and yellow stripes. The colour is on the insulation, not on the copper itself, and it is a safety feature: correct identification prevents the live wire being confused with the neutral or earth. For example, when wiring a three-pin plug you match each coloured core to the correct terminal, and you check the colours again before closing the plug. The same principle applies to flexes, fixed wiring and appliance leads.

What earns the marks

• The insulation is the coloured plastic sleeve around each metal conductor, so the colour identifies the wire without touching exposed copper.
• States the specific UK colour codes: live is brown, neutral is blue, and earth is green and yellow stripes.
• Each core in a mains cable has a different insulation colour, allowing live, neutral and earth to be told apart at a glance.
• Correct colour identification is a safety requirement because connecting a wire to the wrong terminal can make exposed metal parts live.
• Colour coding applies to the whole cable, including the cores inside a three-pin plug and the wires in a lighting circuit.

Common mistakes and how to put them right

• Thinking the copper conductor itself is coloured.

  Put it right: The colour is on the insulation, so the error is corrected by stating that the plastic covering carries the colour.

• Assuming the earth wire is always present in every cable.

  Put it right: Some two-core appliances have no earth, so the correction is that only cables with an earth core show the earth colour.

• Confusing the colours of the live and neutral wires.

  Put it right: Memorise that live is brown and neutral is blue.

Exam tips

• Link each colour to its name and function in one line, for example brown is live, so the answer is easy to mark.
• If asked why colour coding matters, write about safety and correct identification rather than just listing colours.
• When a question shows a plug diagram, trace each coloured core to its terminal and state the colour before the terminal name.