To enable wires to be easily and safely identified, all common wiring safety codes mandate a colour scheme for the insulation on power conductors.
Older installations vary in colour codes, and colours may fade with insulation exposure to heat, light and ageing. As of March 2011, the European Committee for Electrotechnical Standardization (CENELEC) requires the use of green/yellow colour cables as protective conductors, blue as neutral conductors and brown as single-phase conductors.
The United States National Electrical Code requires a green or green/yellow protective conductor, a white or grey neutral, and a black single phase. The United Kingdom requires the use of wire covered with green insulation, to be marked with a prominent yellow stripe, for safe earthing (grounding) connections.This growing international standard was adopted for its distinctive appearance, to reduce the likelihood of dangerous confusion of safety earthing (grounding) wires with other electrical functions, especially by persons affected by red-green colour blindness. In the UK, phases could be identified as being live by using coloured indicator lights: red, yellow and blue.
The new cable colours of brown, black and grey do not lend themselves to coloured indicators.
For this reason, three-phase control panels will often use indicator lights of the old colours.Źródło: https://en.wikipedia.org/wiki/Electrical_wiring
Of course, in this profession you need incredible accuracy and precision and patience and the desire to continue learning, because the people who have just completed their education in this field do not yet have a full picture of the situation and self-repair is not possible and you first have to take internships or practice under an experienced electrician.
An electrical code is a set of regulations for electrical wiring..
The intention of an electrical code is to provide standards to ensure electrical wiring systems that are safe and unlikely to produce either electric shock or fires.Ways in which electrical codes ensure safety include ways to prevent (or mitigate) short circuits, ground faults, and overheating from inadequate current-carrying capacity (ampacity).
Appropriately rated fuses or circuit breakers are used to interrupt a circuit loop whose ampacity is exceeded to avoid overheating of wires or other fixtures.
Electrical codes are usually devised by national or international technical organizations, and adopted as law to make them enforceable.Electrical codes differ based on geographic area.See the following: DIN VDE (German Institute for Standardization) published by DIN-Norms is used in Germany National Electrical Code has been adopted for electrical wiring in the United States and for Mexico, Costa Rica, Venezuela and Colombia IEC 60364 is used as a basis for electrical codes in many European countries Canadian Electrical Code published by the CSA is used in Canada (see Electrical wiring in North America). British Standard BS 7671 is the set of regulations for electrical wiring in the United Kingdom. Australian/New Zealand Standard AS/NZS 3000:2007 Wiring Rules is used in Australia and New Zealand. NF C 15-100 (fr) is used for low voltage installations in France RGIE (fr) (Réglement Général sur les Installations Électriques) is used for installations in Belgium. AREI (nl) (Algemeen Reglement Elektrische Installaties) is used for installations in Flanders, Belgium. Źródło: https://en.wikipedia.org/wiki/Electrical_code