Color-coded wires in a distribution box indicate the function of each wire: live/phase, neutral, or ground, following regional standards like NEC, IEC, or CEC.

Purpose of Color Codes

Color codes are used to identify the function of each wire, ensuring safety, simplifying maintenance, and preventing electrical hazards. They help electricians quickly distinguish between live (phase), neutral, and ground wires, which is critical when working on single-phase or three-phase systems .

Common Wiring Color Codes

IEC (Europe, UK, Asia)

• Single-phase AC:
  • Live/Phase: Brown
  • Neutral: Blue
  • Ground/Earth: Green with yellow stripe
• Three-phase AC:
  • Line 1: Brown
  • Line 2: Black
  • Line 3: Grey
  • Neutral: Blue
  • Ground: Green with yellow stripe
• DC circuits:
  • Positive: Brown
  • Negative: Grey
  • Ground: Green with yellow stripe

NEC (United States)

• Live/Phase: Black, Red, or Blue (depending on phase)
• Neutral: White or Grey
• Ground: Green or bare copper
• Large conductors may use black with colored tape to indicate phase

CEC (Canada)

• Similar to NEC, with minor regional variations
• Red may also be used as a live wire in some installations

Single-Phase vs. Three-Phase Systems

• Single-phase: Typically used in homes, consists of one live wire, one neutral, and one ground wire, supplying ~230V.
• Three-phase: Used in industrial or large buildings, consists of three live wires, one neutral, and one ground wire, supplying ~400V. Each phase has a distinct color for easy identification .

Safety Tips

• Always turn off power before touching wires.
• Do not rely solely on color; verify with a multimeter.
• Older installations may not follow current standards; label wires when mixing old and new wiring .
• Ground wires are always green with yellow stripes in modern standards and should never be used for other purposes . Understanding these color codes ensures safe and efficient work in distribution boxes, whether for residential, commercial, or industrial electrical systems.