Standard Wiring Color Codes
Wiring for AC and DC power distribution branch circuits are color coded for identification of individual wires. In some jurisdictions all wire colors are specified in legal documents. In other jurisdictions, only a few conductor colors are so codified. In that case, local custom dictates the “optional” wire colors.
IEC, AC: Most of Europe abides by IEC (International Electromechanical Commission) wiring color codes for AC branch circuits. These are listed in Table 2.1. The older color codes in the table reflect the previous style which did not account for proper phase rotation. The protective ground wire (listed as green-yellow) is green with yellow stripe.
|Table 2.1: IEC (most of Europe) AC power circuit wiring color codes.|
UK, AC: The United Kingdom now follows the IEC AC wiring color codes. Table 2.2 liststhese along with the obsolete domestic color codes. For adding new colored wiring to existing old colored wiring see Cook.
|Table 2.2: UK AC power circuit wiring color codes.|
US, AC:The US National Electrical Code only mandates white (or grey) for the neutral
power conductor and bare copper, green, or green with yellow stripe for the protective ground. In principle any other colors except these may be used for the power conductors. The colors adopted as local practice are shown in Table 2.3. Black, red, and blue are used for 208 VAC three-phase; brown, orange and yellow are used for 480 VAC. Conductors larger than #6 AWG are only available in black and are color taped at the ends.
Canada: Canadian wiring is governed by the CEC (Canadian Electric Code). See Table 2.4. The protective ground is green or green with yellow stripe. The neutral is white, the hot (live or active) single phase wires are black , and red in the case of a second active. Three-phase lines are red, black, and blue.
|Table 2.3: US AC power circuit wiring color codes|
|Table 2.4: Canada AC power circuit wiring color codes.|
IEC, DC: DC power installations, for example, solar power and computer data centers, use color coding which follows the AC standards. The IEC color standard for DC power cables is listed in Table 2.5, adapted from Table 2, Cook.
|Table 2.5: IEC DC power circuit wiring color codes.|
US DC power: The US National Electrical Code (for both AC and DC) mandates that
the grounded neutral conductor of a power system be white or grey. The protective ground must be bare, green or green-yellow striped. Hot (active) wires may be any other colors except these. However, common practice (per local electrical inspectors) is for the first hot (live or active) wire to be black and the second hot to be red. The recommendations in Table 2.6 areby Wiles.  He makes no recommendation for ungrounded power system colors. Usage of the ungrounded system is discouraged for safety. However, red (+) and black (-) follows the coloring of the grounded systems in the table.
|Table 2.6: US recommended DC power circuit wiring color codes.|
Paul Cook, “Harmonised colours and alphanumeric marking”, IEEWiring Matters, Spring 2004
 John Wiles, “Photovoltaic Power Systems and the National Electrical Code: Suggested Practices”, Southwest Technology Development Institute, New Mexico State University, March 2001