Insulation color

Different wire color schemes.
IEC/NEC AC circuits from top to bottom: L1, L2, L3 refer to ungrounded current carrying conductors. N refers to grounded current carrying conductors. G refers to protective grounding system.
DC circuits from top to bottom: Ungrounded positive, ungrounded negative, grounded conductor, and protective grounding system.

Wires can come with insulation (used for carrying current in a circuit) or without insulation (used for grounding system). If the wires have insulation, it will be possible to choose from a variety of different colors each of which is used to signify the purpose of that wire within an electrical installation. The standards vary from country to country, therefore it is necessary to research the practices in your location. Additionally, the appropriate colors will vary in each country depending upon whether the circuit is alternating current (AC), direct current (DC) and its nominal voltage.

IEC standard for residential AC wiring

• Phase 1 - Brown
• Phase 2 - Black
• Phase 3 - Grey
• Neutral - Blue
• Ground - Green with Yellow Stripe/without insulation

US NEC standard for residential 120/208/240 AC wiring

• Phase 1 - Black
• Phase 2 - Red
• Phase 3 - Blue
• Neutral - White or grey
• Ground - Green/Green with yellow/without insulation

Standard for DC wiring in PV systems

• Ungrounded positive - Red
• Ungrounded negative - Black
• Grounded negative or positive - White or grey
• Ground - Green/Green with yellow/without insulation