Wire Color Code Chart

Reference table for NEC US, IEC international, HVAC thermostat, and automotive 12V wire colors. Match the governing standard for the jurisdiction you are wiring in.

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Reference only — not a wiring design tool. Verify with local code, product markings, and a licensed electrician when required. Disclaimer

Standard Color Function Voltage / System Note
NEC 2023 NFPA 70 (US) Black Hot — ungrounded conductor 120V / 240V AC single-phase (also Phase A in 3-phase) Default color for ungrounded ('hot') conductors in NEC branch circuits. Used for Phase A in 3-phase systems. Re-identified conductors per NEC 200.7 (e.g. white used as hot in a 2-wire cable must be re-identified at every accessible point with black or red tape/paint).
NEC 2023 NFPA 70 (US) Red Hot — second ungrounded conductor / Hot Leg 2 (240V 3-wire) 240V AC (3-wire dryer / range circuits) / Phase B in 3-phase / switched leg Used as the second hot leg in 240V 3-wire branch circuits (dryer, range, water heater). Also Phase B in 3-phase. Common as traveler in 3-way / 4-way switch circuits.
NEC 2023 NFPA 70 (US) Blue Hot — Phase C (3-phase) 120/208V or 277/480V 3-phase Phase C conductor in 3-phase systems. Also common as 4-way switch traveler paired with red (NEC 200.7 re-identification allowed for travelers).
NEC 2023 NFPA 70 (US) Yellow Hot — control / signal / switched leg (per NEC 210.5) 120/240V AC control circuits NEC 210.5(C) calls for system identification at each premises with color or labeling for ungrounded conductors 50V or more. Yellow is widely used for switch legs, fan/light split, and control circuits but is not a NEC-mandated specific color.
NEC 2023 NFPA 70 (US) Orange Hot — High-Leg Delta (B-phase, 240V delta) 120/240V 3-phase delta (high-leg / stinger) Orange identification required for the high-leg (B-phase) of a 240V delta system where the B-phase-to-neutral voltage exceeds 120V (commonly 208V). Per NEC 110.15 and 230.56 (commercial/industrial use).
NEC 2023 NFPA 70 (US) White (or Gray) Neutral — grounded conductor 120/240V AC (grounded conductor) Grounded conductor per NEC Article 200. Must carry the equipment grounding to the service neutral. Three-wire ranges and dryers use white for neutral. Gray may be substituted for white in multiconductor cable to identify neutral at a glance.
NEC 2023 NFPA 70 (US) Green, bare, or Green with Yellow stripe Equipment Grounding Conductor (EGC) All AC systems (grounding / bonding path) Equipment Grounding Conductor (EGC) per NEC Article 250. May be bare copper, insulated green, or green with one or more yellow stripes. NEVER carry current under normal conditions — fault path only. NEC 250.119 lists permitted identification.
NEC 2023 NFPA 70 (US) Black and Red (pair) 3-way switch travelers 120V AC switching leg Traveler conductors between two 3-way switches in a circuit. NEC 200.7(C)(2) prohibits using grounded conductors (white/gray) as travelers — they must be re-identified or replaced with hot colors (commonly black/red).
NEC 2023 NFPA 70 (US) Red and Blue (pair) 4-way switch travelers (in / out) 120V AC multi-way switching Traveler pair on either side of one or more 4-way switches between two 3-way switches. The 4-way switch swaps the traveler pair. Standard convention is red/blue for the traveler pair; always confirm with the device documentation.
IEC 60446 (International AC) Brown Line (L1 / L) — AC phase conductor 230V AC single-phase / L1 in 3-phase (EU, UK, AU, CN) Per IEC 60446 the preferred color for AC line / phase conductor is brown (single-phase L). In 3-phase, brown = L1, black = L2, gray = L3 (per IEC preference, replacing older EU scheme of brown/black/grey).
IEC 60446 (International AC) Blue Neutral (N) — grounded AC conductor 230V AC (EU, UK, AU, CN) Per IEC 60446 blue is the preferred neutral color. WARNING: This is the same color as NEC US 'Phase C' — context (US vs EU) determines the meaning. In mixed-cable assemblies the marking (number / function letter) is the primary identifier.
IEC 60446 (International) Green / Yellow stripe Protective Earth (PE) — equipment grounding All AC systems (fault path) Per IEC 60446 the preferred color for protective earth is a bi-color green/yellow stripe over the entire length. Solid green is no longer preferred (legacy). NEVER carry current under normal conditions — fault path only.
IEC 60446 (DC) Brown (preferred) or Red (legacy) DC Positive (+) conductor Low-voltage DC (12V / 24V / 48V systems) IEC 60446 §6 lists brown as preferred for DC positive conductors (legacy installations use red). Functional Earth (FE) is pink — distinct from PE green/yellow.
IEC 60446 (DC) Light Blue (preferred) or Black (legacy) DC Negative (−) conductor Low-voltage DC (12V / 24V / 48V systems) IEC 60446 §6 lists light blue as preferred for DC negative conductors (legacy installations use black). Same color as IEC AC neutral — context (AC vs DC) determines meaning; per IEC §6.2 the conductor marking (e.g. 'L-', 'M', or function) disambiguates.
HVAC thermostat convention (US 24V) Red (R) R — 24V power from transformer (RED wire) 24V AC thermostat control R terminal / red wire: 24V hot leg from the indoor transformer. RC (red with C jumper) = cooling transformer; RH = heating transformer. Conventional letter code, not a NEC- or IEC-mandated color.
HVAC thermostat convention (US 24V) White (W) W — Heat call (WHITE wire) 24V AC thermostat control W terminal / white wire: closes the circuit to energize the gas furnace or strip-heat relay. Multiple stage systems use W1, W2 for staged heat.
HVAC thermostat convention (US 24V) Yellow (Y) Y — Cooling call (YELLOW wire) 24V AC thermostat control Y terminal / yellow wire: closes the circuit to energize the compressor contactor. Y1 = stage 1, Y2 = stage 2 cooling. Note this conflicts with NEC Phase C / control convention — HVAC letters (Y) and not the wire color is the primary identifier.
HVAC thermostat convention (US 24V) Green (G) G — Fan relay (GREEN wire) 24V AC thermostat control G terminal / green wire: energizes the indoor blower fan relay independent of heating/cooling call. Same color as IEC PE / NEC EGC in branch-circuit work — letter (G) and 24V context is the only differentiator.
HVAC thermostat convention (US 24V) Blue (C) C — Common / 24V return (BLUE wire) 24V AC thermostat control C terminal / blue wire: the 24V common return; powers modern Wi-Fi thermostats that need a constant source. NOT present on legacy 4-wire systems (R/W/Y/G only). Same color as IEC Neutral — context (HVAC 24V) is the differentiator.
HVAC thermostat convention (US 24V) Orange (O) or Blue (B) O/B — Heat pump reversing valve 24V AC thermostat control (heat pump systems) O terminal = energized in COOL mode (most Rheem / Ruud / Bosch heat pumps). B terminal = energized in HEAT mode (most Mitsubishi / Daikin / Fujitsu heat pumps). OEM-specific; always check the heat pump documentation before wiring.
SAE J1128 (Automotive 12V) Red Battery + — always-hot 12V positive 12V DC automotive primary Battery positive cable / always-hot feed to the fuse box. SAE J1128 is the cable spec; OEM wire harness color conventions (red = battery +) are widely but not universally followed.
SAE J1128 (Automotive 12V) Black (or Brown) Chassis ground / 12V negative 12V DC automotive primary Battery negative / chassis ground. Connects to the chassis, engine block, and body. Brown is common in European OEM harnesses for chassis ground per IEC 60446 functional-earth alignment.
SAE J1128 (Automotive 12V) Pink (or Yellow) Ignition-switched 12V positive 12V DC switched accessory Ignition-switched 12V feed. Energized with key in 'run' / 'accessory'. OEM conventions vary — Honda uses yellow for switched ignition, GM often uses pink, Ford uses red/yellow-stripe. Always trace with a multimeter.

How to read this chart

Read across each row left-to-right. Start with Standard to lock the governing document — NEC for US branch work, IEC 60446 for most other regions, the HVAC letter convention for indoor thermostat wiring, or SAE J1128 for automotive 12V. Move to Color for the wire insulation you are holding, then Function for the role that color carries under that standard, then Voltage / System to confirm the system matches your application. The Note column lists caveats: re-identification rules, traveler pairings, and regions where the same color means a different thing. When a single color maps to different roles across standards — blue is Phase C in NEC 3-phase, Neutral in IEC EU, and Common in US HVAC 24V — the standard column and terminal letters disambiguate, not the color alone.

Common scenes

The scenarios below are the bundles of colors you will see in the field. Each scene names the governing reference.

  • Residential 120V branch circuit (US)

    Black (hot) + White (neutral) + Green/bare (EGC). Reference: NEC 2023 Articles 200, 210, 250.

  • Residential 240V 3-wire (US dryer / range)

    Black + Red (both hot) + White (neutral) + Green/bare (EGC). Reference: NEC 2023 Article 210.

  • EU single-phase AC (230V)

    Brown (Line) + Blue (Neutral) + Green/Yellow (PE). Reference: IEC 60446.

  • HVAC 24V thermostat (US)

    R + W + Y + G + C (and O or B for heat pump). Convention only — confirm OEM documentation before wiring.

  • Automotive 12V primary (US/EU)

    Red battery + / Black or Brown chassis ground / OEM-specific switched ignition. Reference: SAE J1128 + IEC 60446 functional earth.

NEC 120V branch — outlet box Outlet Panel Black (hot) White (neutral) Green / bare (EGC) Hot to brass. Neutral to silver. Ground screw on the outlet yoke. Verify with panel labeling and local code. Reference: NEC 2023 Articles 200, 210, 250.
Schematic of a NEC 120V branch circuit: black hot, white neutral, green or bare equipment grounding conductor. Reference: NEC 2023 Articles 200, 210, 250.
HVAC 24V thermostat — R / W / Y / G / C Thermostat R W Y G C Handler R W Y G C R (red) W (white) Y (yellow) G (green) C (blue) R = 24V power, W = heat call, Y = cooling, G = fan, C = common return. Letters are the identifier; wire colors are the cable. Industry convention, no single governing standard — verify with OEM documentation.
Schematic of HVAC 24V thermostat control wiring: R (red) 24V power, W (white) heat call, Y (yellow) cooling, G (green) fan, C (blue) common return. Conventional letter code, not a governing standard — verify with OEM documentation.

Re-identification rules (NEC 200.7)

A conductor whose factory color implies a different function than the role it is being used for must be re-identified. The most common case is a 2-wire cable with black and white conductors repurposed for a 240V branch circuit — the white conductor must be marked with black or red tape or paint at every accessible point, at every junction box, and at every device. NEC 200.7 also prohibits using a grounded conductor (white or gray) as a switch traveler in a 3-way or 4-way circuit — the traveler pair must be re-identified with hot colors (commonly black/red or red/blue) or replaced. Solid green is reserved for equipment grounding under NEC 250.119 — never re-identify a green or bare conductor as a hot or a neutral.

For IEC jurisdictions, conductor function is set at the panel and at the device by the terminal marking (L, N, PE) rather than by on-the-fly color re-marking. If the marking and the color disagree, trust the marking and re-pull the conductor.

When the same color means three things

Blue is the most-confused color on this page. In NEC US 3-phase work it is Phase C; in IEC EU it is the AC neutral; in US HVAC 24V thermostat work it is the C (common / 24V return) terminal. The cable insulation is the same blue in all three settings. The governing standard — not the spool you pulled — sets the meaning. Marking the conductor at every termination (L1/L2/L3, N, PE, or R/W/Y/G/C) is what makes the difference visible at the device.

Green also crosses standards. In NEC US it is equipment grounding (EGC); in IEC it is the protective earth (PE) stripe; in US HVAC 24V it is the G (fan relay) terminal on the thermostat. None of those three roles should ever carry current under normal operation. If any green conductor shows voltage to ground with the circuit energized, stop and call a licensed electrician.

Red is the second-most-confused: NEC hot leg, automotive battery +, IEC DC positive, HVAC R terminal. Same flag — pin the meaning to the standard and terminal letter, not the wire.

Confirm before you energize

Color is a hint, not a guarantee. Use a multimeter or a non-contact voltage tester to confirm the conductor is de-energized before touching it. Verify the panel labeling, the device markings, and the local governing code before connecting. If the building predates the 2023 NEC color update — or if the wiring was added by a previous owner — there is no substitute for a tester. Lock-out / tag-out the breaker, confirm with the meter, and only then work the conductor.

Related pages

Frequently asked

Why is the same wire color different between the US and Europe?

NEC (US) and IEC 60446 (Europe and most international) identify the same conductor function with different colors. In the US, black = hot and white = neutral; in IEC regions, brown = line and blue = neutral. Both are correct under their own code — match the local governing standard first before wiring.

What does the green (or bare) wire mean?

In NEC, green or bare copper is the equipment grounding conductor (EGC) — a safety path back to the panel. In IEC 60446, the equivalent is green/yellow striped insulation. Neither should carry current in normal operation; if it does, stop and diagnose the fault path.

Are the R, W, Y, G, C thermostat wires the same as house wiring colors?

No. Thermostat R/W/Y/G/C/O/B is an industry letter convention, not a governing code. The actual wire colors are the multi-conductor cable stripes — what matters is the terminal letter on the thermostat and the matching terminal on the handler. Cross-check the OEM wiring diagram for your unit before connecting.

Can I use a 2-wire cable with black and white as a 240V circuit?

Not without re-identification. NEC 200.7 requires that any conductor used as an ungrounded (hot) conductor — including in a 240V branch — be re-identified at every accessible point if its factory color implies a different function. A black/white cable run for 240V must have the white conductor re-marked with black or red tape or paint at every junction box. Verify with local code first.

Sources

  • NFPA 70 National Electrical Code 2023 — Article 200: Use and Identification of Grounded Conductors — National Fire Protection Association (NFPA), 2022 (2023 edition). Reference
  • NFPA 70 National Electrical Code 2023 — Article 210: Branch Circuits — National Fire Protection Association (NFPA), 2022 (2023 edition). Reference
  • NFPA 70 National Electrical Code 2023 — Article 250: Grounding and Bonding — National Fire Protection Association (NFPA), 2022 (2023 edition). Reference
  • IEC 60446 — Basic and safety principles for the man-machine interface, marking and identification of conductors — International Electrotechnical Commission (IEC), 2007 (8th edition, current). Reference
  • SAE J1128 — Low-Voltage Primary Cable (12V Automotive) — SAE International (Society of Automotive Engineers), 2023 (current revision). Reference
  • HVAC Thermostat Wiring Color Convention — R/W/Y/G/C/O/B Letter Code (industry convention, no single governing standard) — Industry convention (Honeywell, Ecobee, Carrier, Trane, Lennox OEM documentation cross-reference), 2024 (cross-referenced 2024 OEM install guides). Reference

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