Positive Wire Color (208 VAC)
The acronym VAC is voltage alternating current and represents the voltage that can flow safely through a wire. For example, 208 VAC indicates that the wire can carry up to 208 volts. Although not mandated, the color for the positive, or hot, wire up to 208 VAC generally is black, red or blue; however, it is never white, gray, green or green and yellow striped.
Positive Wire Color (480 VAC)
A wire that is 480 VAC can carry up to 480 volts. The colors commonly used for this type of positive wire are brown, orange or yellow. The wire cannot be white, gray, green or green and yellow striped.
Neutral Wire Color
The color of the neutral, or negative, wire is mandated and must always be white or gray irrespective of the VAC flowing through the wire.
Ground Wire Color
Most electrical circuits have a ground wire so that in the event of an electrical fault there is a direct link to ground the electrical supply. The ground wire for both 208 VAC and 480 VAC can be bare, green or green and yellow striped.
The thickness of electrical wires, whether they are positve or neutral, must exceed the amperes of the electrical circuit. For example, if the appliance the wire connects to uses 12 amperes, then the thickness of the wire must be able to take more than 12 amperes. The standard numbering system in the United States to calculate the type of wire needed is called the American Wire Gauge (AWG).