Home Electrical Wire Color Code Chart: NEC, IEC, and UK Standards Explained

In the US and Canada (NEC/CEC), standard 120/240V residential wiring uses black, red, or blue for hot (line) conductors, white or gray for neutral, and bare copper or green for equipment ground. In the EU, UK, and Australia (IEC standards), brown, black, or gray are hot, blue is neutral, and green-and-yellow is ground. Because mixing these standards or misinterpreting legacy wiring can result in fatal shocks or arc faults, you must verify the standard applicable to your region before touching any terminal.

The Master Home Electrical Wire Color Code Reference Table

The table below maps the primary conductor functions across the four major residential wiring standards. Use this as your bench reference when identifying cables in a junction box, panel, or device backbox.

Note on NM-B Cable Jackets: In the US, the outer jacket color of non-metallic (NM-B) cable is also a standardized indicator of wire gauge and ampacity. White jackets indicate 14 AWG (15A circuits), yellow indicates 12 AWG (20A circuits), and orange indicates 10 AWG (30A circuits). Black jackets are typically used for 8 AWG or larger, or for specialized 600V applications.

Decoding the Rows: Practical Meanings and Common Mistakes

Memorizing the table is only the first step. On the jobsite or inside a crowded 4-gang switch box, wire colors are frequently abused, faded, or repurposed. Here is what each row actually means in practice, followed by the specific scenarios where DIYers and even journeyman electricians make dangerous assumptions.

What Each Function Means in Practice

• Line/Hot: The ungrounded conductor carrying the full source voltage (120V, 230V, or 240V nominal) from the breaker to the load. This wire is always a shock hazard when the circuit is energized.
• Neutral: The grounded conductor. It carries the return current back to the panel. While it is bonded to ground at the main service disconnect, it can carry lethal voltage if a neutral connection is broken upstream while a load is connected.
• Earth/Ground: The equipment grounding conductor (EGC). It carries current only during a fault condition to trip the breaker. It should never carry normal operating current.
• Switched Hot / Traveler: A hot wire that is interrupted by a switch, or one of the two conductors connecting a pair of 3-way switches.

Rows People Get Wrong (And Why)

The Old UK Black Neutral Trap: If you are working in a UK home wired before April 2006, the neutral wire is black. However, black was also frequently used as a switched live in older lighting circuits without proper sleeving. Treating an old UK black wire as a guaranteed neutral without testing it with a multimeter is a leading cause of residential shocks in British retrofits.

Bare Copper as Neutral: In older knob-and-tube wiring or abusive DIY repairs, you may find bare copper used as a neutral. This is a severe code violation and shock hazard. Bare copper is strictly reserved for the equipment grounding conductor in modern NM-B and THHN installations.

3-Way Switch Travelers: The NEC does not mandate specific colors for travelers. However, standard practice uses the red and black wires in a 12/3 or 14/3 cable. If a 12/2 cable was improperly used for a traveler run, the white wire will be acting as a traveler and must be treated as an ungrounded hot conductor.

Handling Faded, Painted, or Unmarked Wires Safely

In older homes, white neutral wires can yellow or brown from heat and age, making them indistinguishable from hot wires. Conversely, black hot wires painted over by careless drywallers can look gray or white. Never trust visual color identification alone if the insulation is compromised, dirty, or faded.

Safe Interpretation Protocols

1. De-energize and Lock Out: Turn off the breaker and use a lockout/tagout device if you are in a shared space.
2. Verify Dead with a CAT III Multimeter: Do not rely solely on a Non-Contact Voltage Tester (NCVT). NCVTs can give false negatives on shielded cables or false positives from phantom voltage. Use a solenoid tester (Wiggy) or a CAT III rated digital multimeter to test Line-to-Neutral, Line-to-Ground, and Neutral-to-Ground.
3. Re-Identify with Phase Tape: Once you have traced and verified the conductors, re-identify them using high-quality vinyl electrical tape (such as 3M Super 33+ or Scotch 35 phase tape). Wrap the tape completely around the wire insulation at least twice, extending slightly past the stripped end so the color is visible when inserted into a wire nut or terminal.
4. Document the Panel: If you discover miscolored wires in a subpanel or junction box, update your panel schedule and leave a note inside the panel cover for the next technician.

Regional Standards: NEC, IEC, and Local Code Authority

Wire color codes are not universal, and applying the wrong regional standard to a local installation is a critical safety failure. Here is how to determine which standard applies to your workbench or jobsite.

When sourcing components or reading wiring diagrams online, always check the origin of the author. A DIY tutorial from the US will show white as neutral, while a tutorial from Germany will show blue. If you are importing smart home relays (like Shelly or Sonoff modules) designed for the EU market into a US home, you must mentally map the device's blue terminal to your home's white neutral wire, and the brown terminal to your black hot wire.

For definitive code requirements, always consult the National Fire Protection Association (NFPA) for US-based NEC guidelines, or the UK Health and Safety Executive (HSE) for IEC/BS 7671 color code transitions. Remember that these resources provide NEC-style and IEC-style guidance; your local Authority Having Jurisdiction (AHJ) or municipal electrical inspector always has the final legal authority on code compliance and permitted color exceptions in your specific municipality.