For single-phase, Black (for 120V) or Red (for 277) is used for Line and Grey is used for Neutral.Earth or protective conductor: Green/Yellow or Green or bare copper conductor. We have a building we are going to wire, and it will have a 480 volt 3 phase 4 wire service, with a step down transformer that will supply 120/240 3 phase 4.The color code adopted in the US is as follows: Primary Voltage: 117Vac 50-60HZ Primary wire color Code: black, black Secondary Voltage: 12Vac 1.5A Secondary wire color Code: white, white Power Rating.
NEC does not instruct any requirements for other conductors. NEC mandates the color codes for neutral and protective ground as grey and yellow-green respectively. National Electrical Code is followed in the United States and sometimes in Canada. For example, you might see yellow wires as switch legs to ceiling fans, structural lights, and outlets paired with light switches. Instead, blue and yellow wires are used as the live wires pulled through a conduit. The above-mentioned color codes are followed in the E uropean Union, United Kingdom, China, Hong Kong, Argentina, Russia, Ukraine, Belarus, Kazakhstan and Singapore. While wires in these colors carry power, they are not used in typical outlet wiring. (of a Positive Grounded) DC Circuit system: (of a Negative Earthed) DC Circuit system:
