Electrical Color Chart: A Complete Guide to US Wire Color Codes

Every year US emergency rooms treat over 30,000 people for electrical injuries — and a meaningful share trace back to misidentified wires in junction boxes. The electrical color chart used in US residential and commercial wiring follows National Electrical Code (NEC) conventions that haven’t changed dramatically in decades, but the system is not universal. International wiring, older homes built before 1965, and three-phase commercial circuits all use different conventions that can trip up a DIYer. This guide covers the standards you’ll see in modern US wiring and how to identify wires safely when colors don’t match the chart.

The US Residential Color Code (Single-Phase 120/240V)

Standard NEC residential wiring follows this color system:

• Black: Hot (ungrounded conductor) — typically the primary hot in 120V circuits
• Red: Secondary hot — used in 240V circuits, three-way switches, and switched outlets
• White: Neutral (grounded conductor) — returns current to the panel
• Bare copper or green: Equipment ground — bonds metal boxes and appliances to earth
• Blue, yellow: Switched hot conductors in conduit installs, sometimes secondary hots

NEC Article 200 mandates white for neutral and green (or bare) for ground. There is no flexibility on those two colors at terminations — even if a cable arrives at the box with an unusual color, the installer must re-mark it with white or green tape at every termination point.

The 120V Circuit Breakdown

A typical 120V outlet circuit uses 14-gauge or 12-gauge NM-B cable (also called Romex). 14/2 NM-B contains a black hot, a white neutral, and a bare copper ground inside a sheath. Strip the outer jacket and you’ll see:

• Black wire to the brass screw on the outlet (hot side)
• White wire to the silver screw on the outlet (neutral)
• Bare copper wire to the green ground screw or grounding pigtail

14/3 cable adds a red wire for three-way switches, two-circuit outlets, or split-wired receptacles. The red carries current under specific conditions controlled by switch positions.

The 240V Circuit Breakdown

240V circuits for electric dryers, ranges, water heaters, and HVAC use two hot conductors instead of one. The color code:

• Black: Hot leg one (120V relative to ground)
• Red: Hot leg two (120V relative to ground, 240V between black and red)
• White: Neutral (only present on circuits that also draw 120V, like ranges with clock/light)
• Bare copper or green: Equipment ground

Pure 240V loads (like a baseboard heater) use 10/2 cable with black and white conductors plus ground. NEC requires re-marking the white conductor with black or red tape at both terminations to indicate it’s being used as a hot, not neutral.

The Three-Phase Commercial Color Code

Commercial buildings use three-phase power instead of split single-phase. The color code depends on voltage:

208Y/120V (most US commercial):

• Black: Phase A
• Red: Phase B
• Blue: Phase C
• White or gray: Neutral
• Green: Ground

480Y/277V (industrial, large commercial):

• Brown: Phase A
• Orange: Phase B
• Yellow: Phase C
• Gray: Neutral
• Green: Ground

NEC mandates the 480V system use these specific colors to prevent voltage misidentification. Touching a 480V conductor expecting 208V is potentially fatal.

Pre-1965 Wiring: Color Codes That Don’t Apply

Houses wired before the mid-1960s often used different conventions:

• Cloth-wrapped wiring (knob and tube): typically two black wires, no ground
• Early Romex: black hot, white neutral, no separate ground
• Aluminum branch wiring (1965-1972): standard colors but aluminum conductor — requires special CO/ALR rated devices
• BX (armored cable): the metal sheath functioned as ground; inner conductors used standard black/white colors

If your home was built before 1965 and you haven’t had it rewired, never assume the colors mean what they do today. Test every conductor with a non-contact voltage tester (Klein NCVT-3P, Fluke 1AC II) before touching anything.

Brand Spotlight: Klein Tools for Wire Identification

Identifying wires safely requires good tools. Klein Tools dominates the US residential electrical trade for one reason: their diagnostic gear is accurate, durable, and reasonably priced. The MM320 multimeter ($35-$45) reads AC and DC voltage to 600V, continuity, resistance, and basic capacitance — enough for 95% of residential troubleshooting. The NCVT-3P non-contact voltage tester ($25) detects 12-1000V AC through insulation without contact.

For more complex work, the Klein ET310 circuit tracer ($120) pairs a transmitter and probe to identify which breaker controls which circuit — invaluable when an electrical panel was labeled wrong by the previous owner or never labeled at all. Combined with the Klein 11055 wire stripper for cutting and stripping multiple gauges, the basic kit costs around $200 and replaces what would have required four separate tools a decade ago. Pair the tools with NEC-compliant color identification tape (Scotch 35 Vinyl Electrical Tape in red, white, green, blue) for relabeling conductors that don’t match the standard chart.

Special Markings You’ll See

Beyond the basic colors, wires in commercial and industrial installs carry additional identification:

• Striped wires (white with red stripe): isolated ground conductors, used in computer and medical installs
• Yellow conductors in industrial: 277V hot in 480/277V wye systems
• Purple, pink, tan: control circuits, low-voltage systems, signal wiring (not standardized by NEC, varies by installer)
• Numbered conductors: in MC cable and conduit, you may see individually numbered THHN wires for circuit identification

If you encounter wiring that doesn’t match any standard chart — old colors, mystery taps, custom labels — turn off the breaker, lock out the panel, and verify de-energized state with a contact voltage tester before working.

Safety Rules That Override the Color Chart

Color codes are a starting point, not a guarantee. NEC 110.7 and 110.12 hold the installer responsible for proper identification regardless of what color appears in the box. Three rules supersede the chart:

1. Always test before touching. Use a voltage tester to confirm de-energized state — color alone never proves a wire is dead.
2. Re-mark any conductor used differently from its color. White used as a hot must be taped black or red at every termination.
3. If in doubt, pull a permit and call a licensed electrician. The cost of an inspection is small compared to the cost of a panel fire or electrocution.

When DIY Is Reasonable and When It’s Not

Replacing a standard 120V outlet, swapping a light switch, or installing a ceiling fan on existing wiring is reasonable DIY territory once you understand the color code. Adding new circuits, working in the main panel, or upgrading service requires a permit and inspection in nearly every US jurisdiction. Most importantly, three-phase commercial work and any project involving 480V power needs a licensed electrician — full stop.

Mastering the electrical color chart for your home’s voltage system, paired with a $30 voltage tester and a healthy respect for the panel, lets you handle the work that genuinely doesn’t need a pro — and recognize the projects that absolutely do.