Positive, Negative and Neutral Wires Color
Color codes for wires helps ensure easy and proper identification of the wire types and safety precautions required. The color of wires is dependent on the method of wiring and where one is located. In the United States, a common two-wire ungrounded circuit has a red positive wire and a black negative wire. For a two-wire system with a negative ground, the positive wire is red, and the negative wire is white. For a two-wire system with a positive ground, the positive wire is white, and the negative wire is black.
As to the neutral wires, the U.S. National Electric code and Canadian Electric Code mandates only white or grey color be used. The International Electrotechnical Commission and countries that abide by it, such as the United Kingdom, use blue for the wiring color code for neutral wire of AC branch circuit. A neutral wire in AC power provides a low-impedance path to earth or ground to prevent passage of heavy voltage through the equipment.