In the US and Canada (NEC), the standard AC color code electrical wire scheme uses black or red for hot (line), white or gray for neutral, and bare copper or green for ground. In Europe and most of the world (IEC), brown is hot, blue is neutral, and green-and-yellow is ground. Never trust color alone on older wiring; always verify with a meter. Below is the complete reference chart.
The Master Electrical Wire Color Code Reference Table
This table covers the primary alternating current (AC) and direct current (DC) wiring standards. Use this as your bench and jobsite quick-reference.
| Function | US / Canada (NEC) | Europe / Global (IEC 60446) | UK (Post-2004 Harmonized) | UK (Pre-2004 Old) |
|---|---|---|---|---|
| AC Hot (Line 1) | Black | Brown | Brown | Red |
| AC Hot (Line 2) | Red | Black | Black | Yellow |
| AC Hot (Line 3) | Blue | Grey | Grey | Blue |
| AC Neutral | White or Gray | Blue | Blue | Black |
| AC Ground (PE) | Bare, Green, or Green/Yellow | Green/Yellow Stripe | Green/Yellow Stripe | Green |
| DC Positive (+) | Red (or Black if ungrounded) | Brown | Brown | Red |
| DC Negative (-) | Black (or White if grounded) | Blue | Blue | Black |
| DC Ground | Bare or Green | Green/Yellow Stripe | Green/Yellow Stripe | Green |
Regional Standards: Which Code Applies to You?
Wire colors are not universal. The insulation color on a spool of THHN or NM-B cable is dictated by the regulatory body governing your region's electrical installations.
The "Rows People Get Wrong" Notes
Color codes look simple on paper, but jobsite realities and specific code exceptions trip up even experienced DIYers. Here are the most common pitfalls:
- The White "Switch Loop" Hot: In older US wiring, a 2-wire cable (black and white) was often run up to a ceiling light switch. The white wire was used to carry the hot feed down to the light. NEC allows this only if the white wire is permanently re-identified with black tape or paint at both ends. If you see a white wire connected to a black wire with a wire nut in a switch box, it is a hot wire, not a neutral.
- The 3-Phase Delta High-Leg (Orange): In a 240V 3-phase delta system with a center-tapped neutral, you get 120V on two phases, but 208V to ground on the third phase (the "high leg" or "wild leg"). NEC 110.15 and 215.8 mandate this high-leg must be colored Orange. Wiring a 120V circuit to an unidentified high-leg will instantly destroy the appliance and cause a fire.
- DC Negative vs. AC Neutral: In automotive and off-grid solar DC systems, black is almost universally negative. In AC home wiring, black is hot. Mixing up AC and DC conventions when wiring a hybrid inverter's AC input vs. DC battery input is a classic way to blow up the inverter's internal MOSFETs.
- Faded THHN in Conduit: Red THHN wire exposed to UV light or high heat in conduit often fades to a pale pink or orange over a decade. Blue can fade to purple. Never assume a faded pink wire is a low-voltage control wire; treat it as a faded red hot wire until proven otherwise.
Safe Interpretation When Markings Are Faded or Missing
When you open a junction box and the wire colors are painted over, faded, or covered in drywall mud, you must abandon the color code and rely on measurement.
The Verification Protocol:
- Test Line-to-Ground: Set your multimeter to AC Voltage. Measure from the unknown wire to a known, verified ground (like a bare copper wire in the same box or a grounded metal box). A reading of ~120V (US) or ~230V (EU/UK) means the wire is a Hot (Line) conductor.
- Test Neutral-to-Ground: Measure from the suspected neutral to ground. It should read very close to 0V (typically < 2V under load). If it reads line voltage, the "neutral" is actually a hot wire, or you have a severe open-neutral fault upstream.
- Test Switched Legs: If a wire reads 0V to ground, but reads ~120V/230V to a known hot wire, it is likely a neutral or a switched leg that is currently in the "off" position. Toggle the wall switch and re-test to ground. If it jumps to line voltage, it is a switched hot.
Decision Path: Identifying an Unknown Wire
Use this decision tree when you encounter a wire with missing, faded, or non-standard color coding. Follow the steps sequentially to reach a definitive identification and corrective action.
| Condition / Measurement | Diagnostic Result | Required Action (Concrete Pick) |
|---|---|---|
| Reads ~120V/230V to known ground. | Wire is an ungrounded Hot (Line) conductor. | Wrap the wire with 3M Super 33+ Black Vinyl Tape at both ends and label it "HOT". If it's a switch leg, use Red tape. |
| Reads 0V to ground, but continuity to the neutral bus bar with power OFF. | Wire is a grounded Neutral conductor. | Leave as-is if white/gray/blue. If it's black or another color, wrap with White Vinyl Tape to re-identify as neutral per NEC 200.6. |
| Reads 0V to ground, 0V to neutral, but has continuity to a light fixture terminal. | Wire is a Switched Hot (currently OFF). | Turn power on, flip switch. If it reads line voltage, wrap with Red Vinyl Tape to identify as a switched hot leg. |
| Reads 208V to ground in a 3-phase panel. | Wire is a High-Leg Delta conductor. | Immediately de-energize. Re-identify with Orange Vinyl Tape or heat shrink. Do not connect to any 120V breakers. |
| Wire is green/yellow stripe in a DC solar array. | Wire is an Equipment Grounding Conductor (EGC). | Terminate to the DC ground busbar using a ratcheting crimp tool and an appropriately sized ring terminal (e.g., 10 AWG ring for #10 wire). |
By strictly following measurement protocols and re-identifying non-standard wires with high-quality vinyl tape (never use cheap masking tape or duct tape, which degrades and leaves residue), you ensure the next person working on the circuit—whether it is you in five years or a licensed electrician—can trust the color code electrical wire standards in your installation.
