Wire a plug wrong, and you risk a dead short, a shocked user, or a fried appliance. The correct plug wire color code depends entirely on your region's governing standard—primarily the US NEC, the international IEC, or the legacy UK system. Before you strip your first wire or crimp your first terminal, you need to know exactly which standard applies to your cord and receptacle. Here is the exact reference data.
Master Plug Wire Color Code Reference Table
The table below maps the standard conductor functions to their required insulation colors across the four major wiring regimes you will encounter on the bench or in the field. Always verify the cord jacket printing (e.g., SJT, H05VV-F) to confirm which standard the manufacturer followed.
| Function | Symbol | US/Canada (NEC 120V) | US/Canada (NEC 240V) | EU/Intl (IEC 60446) | UK (Post-2004) | UK (Pre-2004 Legacy) |
|---|---|---|---|---|---|---|
| Line 1 (Hot) | L | Black | Black | Brown | Brown | Red |
| Line 2 (240V Hot) | L2 | Red | Red / Black (taped) | Black | Black | Yellow |
| Neutral | N | White / Grey | White / Grey | Blue | Blue | Black |
| Earth / Ground | E / G | Bare / Green | Bare / Green | Green-Yellow | Green-Yellow | Green |
Rows People Get Wrong (And Why It Matters)
- The UK Pre-2004 Black Neutral vs. IEC Black Line 2: This is the most dangerous collision in international wiring. If you are repairing an old UK appliance (where black is neutral) and splice it to a modern IEC cord (where black is a 230V live phase), you will energize the appliance chassis or blow the neutral fuse. Always trace the wires with a meter when working on legacy UK gear.
- US 240V White Conductors: In fixed branch circuit wiring (like NM-B cable to a water heater), the NEC allows a white wire to be used as a hot leg if it is permanently re-identified with black tape at both ends. However, in flexible plug cords (like a dryer cord), white is strictly reserved for the neutral. Never use a re-marked white wire as L2 in a plug.
- Green-Yellow Stripes: Under IEC and modern UK standards, green with a yellow stripe is exclusively for earth/ground. It must never be used for a switched live or a low-voltage DC signal in a hybrid harness.
Regional Pinouts and What the Symbols Mean in Practice
Color codes only get you halfway there. You also need to map those colors to the correct physical pins on the plug. The symbols stamped into plug terminals—L, N, and E (or G)—dictate this mapping.
US & Canada: NEMA 5-15 and 6-20 Standards
Governed by NFPA 70 (the NEC), North American plugs rely on physical asymmetry to enforce polarity.
- L (Line/Hot): Connects to the brass screw. The plug blade is narrow. This carries the 120V nominal (114-126V acceptable) potential relative to ground.
- N (Neutral): Connects to the silver screw. The plug blade is wide. This is the grounded current-carrying conductor.
- G (Ground): Connects to the green screw. The pin is the U-shaped or round peg. This provides equipotential bonding—a safety path connecting all exposed metal parts of the appliance to the same zero-voltage potential to prevent shock during a fault.
UK: BS 1363 Standard
The UK 3-pin plug is a marvel of mechanical safety engineering. According to UK Health and Safety Executive guidelines, the pinout is strictly defined:
- E (Earth): The longest pin at the top. It is mechanically linked to internal shutters; inserting the earth pin first opens the shutters for the L and N pins. Connects to the green-yellow wire.
- L (Line): Bottom right pin (when looking at the plug face with the earth pin up). Connects to the brown wire. Must be protected by an internal BS 1362 ceramic or sand-filled fuse.
- N (Neutral): Bottom left pin. Connects to the blue wire.
Europe: CEE 7/7 (Schuko / Type F)
Standardized under NEMA and international IEC frameworks, the Schuko plug is unique because it is unpolarized—it can be plugged in upside down. Therefore, while the cord colors (Brown=L, Blue=N, Green-Yellow=E) remain strict, the L and N pins on the plug itself are interchangeable. The earth connection is made via metal clips on the top and bottom edges of the plug face, not a dedicated pin.
Safe Interpretation for Faded or Non-Standard Cords
Never trust the jacket color on a cord pulled from a bin, a cheap imported replacement, or an appliance that has been sitting in a damp garage for a decade. UV exposure, heat, and cheap manufacturing can result in faded insulation or outright wrong colors (e.g., a cord where all three internal wires are black). Here is how to safely interpret and verify the wiring before applying power.
In older homes or poorly repaired equipment, you may encounter a "bootleg ground"—a hidden jumper wire connecting the neutral blade to the ground pin inside the plug. This fools a standard 3-light receptacle tester into showing a "correct" wiring status, but it leaves the appliance chassis energized at 120V if the neutral wire breaks upstream. Always verify ground integrity with a multimeter, not just a plug-in tester.
The Multimeter Verification Protocol
Grab your digital multimeter (DMM) and set it to the continuity or resistance (Ω) setting. Perform this 3-step check on any untrusted cord:
- Map the Pins: Touch one probe to the physical Ground pin (or earth clips) on the plug, and the other probe to each stripped wire end. The wire that reads < 1 ohm (and beeps) is your Earth/Ground. Mark it with green tape.
- Identify the Hot/Neutral: Touch the probe to the narrow blade (US) or the L-labeled pin (UK/EU). Find the wire end that reads < 1 ohm. Mark it black (US) or brown (IEC). The remaining wire should show continuity only to the wide blade or N pin. Mark it white or blue.
- Check for Shorts and Bootlegs: Set your DMM to the highest resistance range (usually 20MΩ or 200MΩ). Measure between all three wire ends. The reading must be OL (Over Limit) or > 10MΩ. If you read near 0 ohms between the Neutral and Ground wire ends, you have a short or a bootleg jumper. Cut the plug off and discard it.
By relying on physical pin mapping and continuity testing rather than visual color assumptions, you eliminate the risk of cross-wiring international equipment. When in doubt, cut back the jacket, strip fresh copper, and let the multimeter dictate the color tape you apply.
