Color codes tell you the role of each conductor, but there isn’t a single global standard. In many regions, hot wires are black or red (or brown in some systems), neutrals are white (US) or blue (EU), and grounds are green or bare. Other colors mark special purposes or multiple hot conductors. This guide outlines the most common conventions by region and use, with cautions to check local codes and labels.
Wiring color schemes vary by region, voltage level, and purpose—ranging from household mains and low‑voltage DC power to automotive wiring and data cables. The sections below lay out typical mappings and highlight important caveats, so you can identify conductors more confidently and safely.
North America: Household mains (120/240V)
Common practical uses
In typical North American branch circuits and NM cable, the following color roles are standard. Keep in mind that multi‑wire circuits and certain devices may introduce other colors for specific purposes.
- Black — hot (live) conductor carrying current from the power source to the load.
- Red — hot conductor used as a second live in 240 V circuits or for switch legs and multi‑wire branch circuits.
- White — neutral, returning current back to the panel (grounded conductor).
- Green or bare copper — equipment grounding conductor for safety.
- Blue or Yellow — additional hot conductors in some multi‑conductor cables (e.g., for ceiling fans or 3‑way switch legs). Not used as neutral in standard practice unless specifically marked.
Note: If a white or gray conductor is ever used as a hot, it must be re‑identified at terminations with a color such as black, red, or blue, per electrical code requirements.
Europe and many other regions: IEC/EN standards
Common practical uses
Most European and many other jurisdictions follow brown for live, blue for neutral, and green/yellow for earth in new installations. Older systems and some national variations exist, so it’s important to verify locally.
- Brown — live (phase) conductor in most new installations.
- Blue — neutral conductor.
- Green-yellow — protective earth (ground).
- Older UK and some legacy systems: Red — live, Black — neutral, Green-yellow — earth. For three‑phase systems, L1/L2/L3 can be brown/black/grey (with blue as neutral in many cases) depending on country.
Three‑phase differences and regional practice mean you should always consult local wiring diagrams or a licensed electrician when working on installations.
Low‑voltage DC power and electronics
Common practical uses
DC circuits and most electronics use simple, widely adopted color cues. However, variations exist across manufacturers and standards.
- Red — positive (+) supply in many DC power applications.
- Black — negative (−) or ground in most DC systems.
- White or Blue — may be used for negative or signal lines in some devices; always check the device’s documentation or labeling.
Because DC color conventions can vary by device or supplier, confirm polarity on the equipment label or in its service manual before connecting power.
Automotive and specialized wiring
Common practical uses
Automotive and some specialized wiring use manufacturer‑dependent codes, but a few patterns recur across many makes. Do not rely on color alone for critical circuits.
- Red — positive power supply (battery/ignition) in many circuits.
- Black — ground.
- Yellow — often used for constant power or specific accessory circuits (varies by vehicle).
- Blue — sometimes used for accessory or lighting circuits, or for specific control signals; colors can differ by model/year.
- White/Green — may be used for data, sensors, or specialized channels; always verify with the vehicle’s wiring diagram.
Because automotive harnesses are highly manufacturer‑specific, wiring diagrams should be consulted for precise color meanings before any work.
Data and communications cables
Common practical uses
Data cables rely on standardized color pairings to preserve signal integrity. Here are two widespread examples you’re likely to encounter.
- Ethernet twisted‑pair (TIA‑568): Four color pairs—White/Orange with Orange, White/Green with Green, White/Blue with Blue, White/Brown with Brown. The exact pair order depends on whether you’re using T568A or T568B wiring.
- USB cables: Red — +5V, Black — Ground, White — Data−, Green — Data+ (these colors are standard for most USB cables, though some variations exist for charging cables).
When working with data cables, maintain proper pair integrity and consult device or cable specifications for any deviations from the standard color scheme.
Summary
Wire color codes serve as a quick guide to what a conductor does, but they’re not universal. Hot, neutral, and ground roles are the core distinctions, yet regional norms, installation age, and application (mains, DC electronics, automotive, data) create variations. Always verify with local codes, labeling on cables, and manufacturer documentation, and when in doubt, consult a licensed electrician or qualified technician.