Wire / Pipe / Gas Color Codes
NEC, IEC, gas piping, and ASME A13.1 conventions in plain English.
Reference
NEC residential phase (US)
- Phase A (single-phase 120/240) Black
- Phase B (single-phase 120/240) Red
- Neutral (grounded) White or gray
- Equipment grounding conductor Green or bare
- Phases A / B / C, 208Y/120 three-phase (convention) Black / red / blue
- Phases A / B / C, 480Y/277 three-phase (convention) Brown / orange / yellow
IEC industrial (Europe / Australia)
- Line L1 / L2 / L3 Brown / black / gray
- Neutral Blue
- Protective earth (PE) Green and yellow
Gas piping (US trade markings)
- Natural gas Yellow
- Liquefied petroleum (LP) Yellow with markings
- Medical gas oxygen Green
- Medical gas vacuum White
HVAC piping (ASME A13.1)
- Chilled water supply Green with white letters
- Steam Yellow with black letters
- Compressed air Blue with white letters
- Fire suppression water Red with white letters
Checked against published worked examples from: NEC + APWA + project bundled color-code systems.
Details, formula, and sources
Formula or table(reference page; no compute) NEC conductor color conventions, IEC three-phase color conventions, and ASME A13.1 piping identification color scheme.
Source and editionNEC 2023 (NFPA 70). Sections 200, 210, 215, 250 by section. ASME A13.1-2020 by name. IEC 60446 (replaced by IEC 60445) by name.
Free accessFree read-only access at nfpa.org/freeaccess. ASME A13.1 licensed; pipe-marking guides free at most state-DOT and pipe-marker manufacturer (Brady, Seton) sites.
What governsEstimate. AHJ and licensed professional govern.