The Complete Electric Wire Color Chart: NEC vs IEC Standards

When you strip back a piece of NM-B cable or pull THHN through conduit, the insulation color is not just for organization—it is a strict safety and code compliance identifier. In the United States, the National Electrical Code (NEC) mandates specific colors for grounded, ungrounded, and equipment grounding conductors. Across the UK and EU, the IEC 60446 standard enforces a completely different palette. Mixing these up during a panel upgrade or international machine import can result in dead shorts, equipment failure, or lethal shock hazards.

The direct answer for US residential AC wiring: Black, Red, and Blue are hot (ungrounded), White or Gray are neutral (grounded), and Green or Bare Copper are ground (equipment grounding). For UK/EU systems: Brown, Black, and Gray are hot, Blue is neutral, and Green-Yellow is ground.

How to Read the Standard Electric Wire Color Chart

The table below maps the most common AC power functions to their required insulation colors under both the US NEC and the international IEC standards. Before pulling wire, you must understand how to read the temperature and insulation columns, as they directly dictate your ampacity limits.

Bookmark-Friendly Quick Jumps: The two most queried values by DIYers and apprentices are the Neutral Conductor and the Equipment Ground. Always verify these first when tracing an unknown circuit.

Source: NFPA 70 (National Electrical Code) Article 200, 210, and 250; IEC 60446.

Derating, Temperature Columns, and Ampacity Limits

A common mistake among hobbyists and junior electricians is looking at the wire color and ignoring the insulation type stamped on the jacket. The insulation type (e.g., THHN, XHHW-2) dictates the temperature column you must use when calculating ampacity and applying derating factors.

Which Column Applies to Your Installation?

If you are terminating a 90°C rated THHN wire onto a standard residential breaker or receptacle, you are almost always bound by the 60°C or 75°C column. According to NEC 110.14(C), your final ampacity cannot exceed the lowest temperature rating of any connected component, conductor, or device. Since most standard residential breakers and receptacles are rated for 75°C (and some older or specific lighting fixtures are 60°C), you must size your breaker based on the 75°C column, even though the wire itself can physically handle 90°C.

How Derating Rows Modify the Base Value

When you pull multiple current-carrying conductors (CCCs) through a single conduit, they generate heat that cannot dissipate. NEC 310.15(C)(1) requires you to derate the ampacity based on the number of CCCs. Here is how the derating rows modify your base value:

• 4 to 6 CCCs: Multiply the base ampacity by 80%.
• 7 to 9 CCCs: Multiply the base ampacity by 70%.
• 10 to 20 CCCs: Multiply the base ampacity by 50%.

The Professional Trick: You are permitted to use the 90°C column as your starting base value for derating calculations, provided the wire insulation is rated for it. For example, if you have 12 AWG THHN (rated 30A at 90°C) and you pull 5 CCCs in a conduit, you derate to 80%: 30A × 0.80 = 24A. However, your final overcurrent protection (breaker) still cannot exceed the 75°C termination limit (which is 25A for 12 AWG), meaning a 20A breaker is required to remain fully compliant.

What the Electric Wire Color Chart Cannot Tell You

While the chart above covers the baseline standards, real-world jobsite conditions and specific circuit topologies introduce edge cases that a simple color chart cannot address. Relying solely on the chart without understanding these exceptions will lead to failed inspections.

1. Re-identification of Neutral and Traveler Wires

The NEC strictly forbids using a white or gray wire as an ungrounded (hot) conductor unless it is permanently re-identified at every point where it is accessible. If you are wiring a 3-way switch loop or an switch loop to a ceiling fan, and you use a 2-wire NM-B cable (Black and White), the white wire is acting as a hot feed. You must wrap it with black or red phasing tape at both the panel and the switch box. Conversely, if you use a white wire as a traveler in a 4-way switch setup, it must be re-identified with colored tape to indicate it is not a neutral.

2. Multi-Wire Branch Circuits (MWBC)

In an MWBC, you share a single white neutral wire between two hot legs (typically Black and Red) that are on opposite phases of a 120/240V split-phase system. The color chart tells you Black and Red are hot, but it does not tell you that these two breakers must be handle-tied (or use a 2-pole breaker) per NEC 210.4(B). If they are not tied, an electrician could turn off the Black leg to work on a receptacle, not realizing the shared White neutral is still carrying return current from the live Red leg, resulting in a fatal shock hazard.

3. DC Power and Low Voltage Control Colors

The standard AC electric wire color chart does not apply to DC systems like solar arrays, 12V automotive, or 24V HVAC control boards.

• DC Power: Red is universally Positive (+), and Black is Negative (-). In some 48V telecom or solar setups, Blue is used for negative/ground.
• HVAC Control (24VAC):strong> Thermostat wires use a different de-facto standard: Red (R - 24VAC power), White (W - Heat), Yellow (Y - Cooling), Green (G - Fan), and Blue/Black (C - Common). Never assume a blue wire in a thermostat bundle is a 3-phase hot leg.