difference between american wire gauge and standard wire gauge
Standard wire gauge SWG was fixed by Order of Council August 23, 1883. It was constructed by improving the Birmingham Wire Gauge. It was made a legal standard on March 1, 1884 by the British Board of Trade. SWG is not to be confused with American Wire Gauge which has a similar but not quite interchangeable numbering scheme.
Electrical wiring In the United States, color-coding of three-phase system conductors follows a de facto standard, wherein black, red, and blue are used for three-phase 120/208-volt systems, and brown, orange, and yellow are used in 277/480-volt systems. In buildings with multiple voltage systems, the grounded conductors (neutrals) of both systems are required to be identified and made distinguishable to avoid cross-system connections. Most often, 120/208-volt systems use white insulation, while 277/480-volt systems use gray insulation, although this particular color code is not currently an explicit requirement of the NEC.[3]