Electrical Wire Color Codes Explained
Electrical wire colors identify each conductor by its function: black and red are hot (live) wires carrying current, white is neutral (return path), and green or bare copper is the equipment ground (safety path). These colors are standardized by the National Electrical Code (NEC) and are not decorative. Connecting wires incorrectly based on color creates shock hazards, fire risks, and code violations. Here is what every color means and when you will encounter each one.
Standard Residential Wire Colors
Black: Hot
Black wires are the primary hot conductors in residential wiring. They carry electrical current from the breaker panel to outlets, switches, and appliances. Black wires are always considered energized and should never be touched without first confirming the circuit is de-energized at the breaker. In a standard 120V circuit using 14/2 or 12/2 NM-B cable, the black wire is the single hot conductor.
Red: Hot (Second Hot)
Red wires are the second hot conductor in 240V circuits and three-way switch configurations. In a 240V circuit (such as a dryer or range circuit using 10/3 or 6/3 NM-B), both the black and red wires are hot, each carrying 120V on opposite phases to create 240V between them. In three-way switch wiring, the red wire serves as the traveler between the two switches. Like black wires, red wires are always considered energized.
White: Neutral
White wires are neutral conductors that provide the return path for current back to the electrical panel. The neutral carries current during normal operation and is bonded to the grounding system at the main panel. While neutral wires carry current and should be treated with caution, they are at or near zero voltage under normal conditions. In some switch configurations, a white wire may be re-identified with black tape to serve as a hot conductor. This is code-compliant when properly marked.
Green or Bare Copper: Ground
Green insulated wires and bare (uninsulated) copper wires are equipment grounding conductors. The ground wire provides a safety path for fault current to flow back to the panel and trip the breaker if a hot wire contacts a metal enclosure, conduit, or other conductive surface. The ground wire does not carry current during normal operation. It only activates during a fault condition. In NM-B cable, the ground is typically bare copper. In conduit systems, individual green THHN conductors are used.
Additional Colors in Conduit Systems
Blue: Hot
Blue wires are used as hot conductors in conduit wiring, typically for the second hot leg of a three-phase system or as a designated switch leg. Blue is not found in standard NM-B residential cable but is common in commercial installations and residential conduit work.
Yellow: Hot
Yellow wires serve as hot conductors in conduit, often designated for switch legs or the third hot conductor in three-phase systems. Like blue, yellow is primarily used in conduit installations rather than standard residential cable.
Orange: Hot (High-Voltage)
Orange wires are sometimes used to identify the “wild leg” or high-leg delta conductor in certain three-phase systems, carrying a higher voltage relative to ground than the other phases. This is a commercial and industrial application rarely encountered in residential work.
NM-B Cable Jacket Colors
In addition to conductor insulation colors, the outer jacket of NM-B (Romex) cable is color-coded by gauge. White jacket contains 14 AWG conductors (15-amp circuits). Yellow jacket contains 12 AWG conductors (20-amp circuits). Orange jacket contains 10 AWG conductors (30-amp circuits). Black jacket contains 8 AWG or 6 AWG conductors (40-amp or 50-amp circuits). Gray jacket indicates UF-B underground feeder cable, regardless of gauge.
Safety Reminder
Wire color codes are a guide, not a guarantee. Always use a voltage tester to verify that a wire is de-energized before touching it, regardless of its color. Previous work by unqualified individuals may have used incorrect colors or re-identified wires without proper marking. When in doubt, hire a licensed electrician to evaluate the wiring.
IB Lighting carries color-coded NM-B cable, THHN individual conductors in all standard colors, and UF-B cable for every residential and commercial application. Call (800) 674-9019 for pricing, or browse our wire and cable inventory.