Knowing what you work with is important when you undertake a home project. This could never be truer than when working with electricity. Understanding how to approach the electrical board and how to handle each wire can save you from serious injury and even fatality. Knowing what wire colours mean is essential. Always use caution when working with live electrical currents.
A green electrical wire signifies that it is a protective ground wire. A ground wire is grounded to the earth and acts as the backup wire in the event the neutral wire fails. Green wires are not used for any purpose other than grounding.
White or Gray
An electrical wire that is white or grey is a neutral wire, meaning it is connected to earth, like a green wire. A white or grey wire, however, carries electric current in a circuit away from a device. In some situations that require more than one "hot" wire -- a wire that carries an electric current directly from the power source, though, a second white wire may be used as a live wire. In these cases, the end of the wire should include a layer of black electrical tape to alert electricians and other people that the wire conducts electricity.
Black and Red
A black wire is a "hot" wire, carrying an electric current directly from the power source. A red wire is a secondary "hot" wire. Never touch these wires unless you verified that the power source was disconnected or turned off. Red and black wires should never be used for neutral connections.
Orange and Yellow
Orange and yellow wires are used for 480 VAC, meaning they use three-phase medium voltage (4160V) as well as three-phase 480 voltage. Both orange and yellow wires are live wires and are mostly used as switch legs; these wires become hot when the terminal is turned on and power flows.
A blue wire is a hot wire. It is most commonly used as a switch leg that runs power to light switches, ceiling fans and various other ceiling light fixtures. Blue wires are common, with power travelling in three- and four-way switch applications.