If you are wiring a standard US residential or commercial circuit, the direct answer for your wiring color code chart lookup is governed by NFPA 70 (the National Electrical Code, or NEC). For standard 120/240V split-phase systems, use Black or Red for ungrounded (hot) conductors, White or Gray for grounded (neutral) conductors, and Green, Green/Yellow, or Bare Copper for equipment grounding conductors.
Misidentifying a wire color isn't just a code violation; it is a primary cause of fatal shock hazards and arc faults during panel maintenance. This reference guide provides the exact matrix for 120V, 240V, and 3-phase systems, a concrete decision tree for your next pull, and the specific derating modifications you must apply when bundling conductors.
The Master NEC Wiring Color Code Chart
| Circuit Function | 120/240V Split-Phase (Residential) | 120/208V 3-Phase (Commercial Wye) | 277/480V 3-Phase (Industrial Wye) | 240V High-Leg Delta |
|---|---|---|---|---|
| Hot 1 (Ungrounded) | Black | Black | Brown | Black |
| Hot 2 (Ungrounded) | Red | Red | Orange | Orange (High Leg / 208V to Ground) |
| Hot 3 (Ungrounded) | N/A | Blue | Yellow | Blue |
| Neutral (Grounded) | White or Gray | White or Gray | Gray (White prohibited) | White or Gray |
| Equipment Ground | Green, Green/Yellow, or Bare | Green, Green/Yellow, or Bare | Green, Green/Yellow, or Bare | Green, Green/Yellow, or Bare |
Decision Tree: Picking the Right Wire for Your Circuit
Use this decision path to terminate your wire selection process with a concrete pick. Do not guess; follow the logic based on your panel's voltage.
| If Your Installation Is... | Then You Must Use... | Concrete Product Pick (NM-B / THHN) |
|---|---|---|
| Standard 120V, 15A Receptacle | Black (Hot), White (Neutral), Bare (Ground) | 14/2 NM-B Cable (Southwire) |
| Standard 120V, 20A Kitchen/Bath GFCI | Black (Hot), White (Neutral), Bare (Ground) | 12/2 NM-B Cable (Southwire) |
| 240V, 30A Dryer or Water Heater | Black (Hot 1), Red (Hot 2), White (Neutral), Bare (Ground) | 10/3 NM-B Cable (Southwire) |
| 240V, 50A Range or EV Charger | Black (Hot 1), Red (Hot 2), White (Neutral), Bare (Ground) | 6/3 NM-B Cable or 6 AWG THHN in conduit |
| 3-Way Switch Loop (Travelers) | Red and Black (Travelers), White (Re-identified as Hot with black tape) | 14/3 NM-B Cable (Southwire) |
How Derating Rows Modify the Base Value
A common point of confusion is how ampacity derating intersects with wire color codes. Derating modifies the base ampacity value (and thus the required AWG size), not the color code itself. However, when derating forces an upsizing of the conductor, the color requirements remain strictly locked to the voltage phase.
According to OSHA 1910.304 and NEC 310.15(C)(1), when you bundle more than three current-carrying conductors in a single raceway, you must apply a derating factor.
- The Modification: If you pull four 12 AWG THHN hot wires (Black, Red, Blue, Yellow) through a single conduit for two 20A circuits, the base ampacity of 12 AWG (30A at 90°C) is derated by 80%. 30A x 0.80 = 24A. This still safely covers a 20A breaker.
- The Trap: If you pull seven current-carrying conductors, the derating factor drops to 70%. 30A x 0.70 = 21A. You are now dangerously close to the 20A continuous trip curve. You must upsize to 10 AWG THHN.
- The Color Rule: When you upsize to 10 AWG to compensate for derating, you must maintain the exact same color matrix (Black, Red, Blue, Yellow for hots). You cannot switch to White or Gray to save money at the supply house, as those colors are legally reserved for grounded neutrals (NEC 200.6).
What This Chart Cannot Tell You
While the NEC matrix is the legal baseline, a static chart has blind spots that will get you in trouble if you don't account for field realities:
- Legacy Knob-and-Tube or Cloth Wiring: In homes built before 1960, insulation colors have faded to uniform gray/brown. Furthermore, early installers frequently used white wires for hot legs. Never trust color in a pre-1970 panel without verifying with a non-contact voltage tester and a multimeter.
- Switch Loops and Re-identification: The chart says White is Neutral. But in a standard switch loop, a 2-wire cable (Black and White) runs to the switch. The White wire is used to carry switched hot power back to the light. NEC 200.7(C)(2) requires you to re-identify this white wire with black paint or black electrical tape at both terminations. If you leave it white, the next electrician will assume it's a neutral and short the circuit.
- Local AHJ Amendments: Some municipalities (notably Chicago and parts of New York) require all wiring to be in metallic conduit (EMC/Rigid) and ban NM-B cable entirely. While the color codes for THHN remain the same, the materials you buy from the chart's product picks will be rejected by the local inspector.
- Multi-Wire Branch Circuits (MWBC): If you are sharing a neutral (White) between two hot legs (Black and Red) on a 120/240V system, the two hot breakers must be on opposite phases (240V between them) and tied together with a handle tie (NEC 210.4). If you accidentally put Black and Red on the same phase, the shared White neutral will carry the sum of both loads, overheat, and melt inside the wall.
Default Recommendation and Concrete Picks
For 95% of residential DIY and professional branch-circuit rough-ins in the US, you do not need to overthink the matrix. Stick to standard NM-B (Romex) for in-wall cavities and THHN in EMT conduit for exposed runs.
The Concrete Pick: Buy Southwire SIMpull NM-B in 250ft coils. For 15A lighting and general receptacle circuits, use 14/2 (Black, White, Bare). For 20A kitchen, bathroom, and garage GFCI circuits, use 12/2 (Black, White, Bare). For 240V baseboard heaters or EV chargers, use 10/2 or 6/2 (Black, White re-taped as Red, Bare).
Do not deviate from these colors to use leftover scrap wire. The cost of a $40 spool of correctly colored wire is infinitesimal compared to the cost of a failed inspection or a miswired 240V fault. Always de-energize the panel, lock out the main breaker, and verify zero voltage with a CAT III rated multimeter before stripping any insulation.
