All common wiring safety codes mandate a colour scheme for the insulation on power conductors enable wires to be easily and safely identified. In a typical electrical code, some colour coding is mandatory, while some may be optional. Many local rules and exceptions exist. Older installations vary in colour codes, and colours may shift with insulation exposure to heat, light, and aging.
Many electrical codes now recognize (or even require) the use of wire covered with green insulation, additionally marked with a prominent yellow stripe, for safety grounding (earthing) connections. This growing international standard was adopted for its distinctive appearance, to reduce the likelihood of dangerous confusion of safety grounding wires with other electrical functions, especially by persons affected by red-green colour blindness.
