For standard AC power plugs and appliance cords, the wire plug color code depends entirely on your region's governing standard. In the US and Canada (NEC), a standard 120V plug uses Black (Hot), White (Neutral), and Green/Bare (Ground). In Europe, the UK, and most IEC-aligned regions, the standard is Brown (Live/Hot), Blue (Neutral), and Green-Yellow (Earth/Ground). Never assume universal color coding; always verify the standard stamped on the plug or appliance inlet before terminating.
Complete Wire Plug Color Code Reference Table
The table below maps the functional role of each conductor to its mandated insulation color across the three major global standards. Use this as your primary bench reference when stripping and terminating replacement cords.
| Function | US/Canada (NEC 120V) | US/Canada (NEC 240V Split) | EU/Global (IEC 60446) | UK (Post-2004) | UK (Pre-2004 Legacy) |
|---|---|---|---|---|---|
| Line / Hot 1 | Black | Black | Brown | Brown | Red |
| Line / Hot 2 | N/A | Red | Black (if 2-phase) | Black (if 2-phase) | Yellow |
| Neutral | White | White | Blue | Blue | Black |
| Earth / Ground | Green, Green-Yellow, or Bare | Green, Green-Yellow, or Bare | Green-Yellow | Green-Yellow | Green |
Regional Variants and the "Rows People Get Wrong"
Miswiring a plug rarely trips a breaker immediately; it creates a latent shock hazard or reverses polarity, which can destroy switch-mode power supplies that rely on a neutral reference. Here is where DIYers and junior technicians consistently misinterpret the table above.
The US White vs. IEC Blue Confusion
In US residential wall wiring (NM-B/Romex), white is strictly neutral. However, in some US switch loops, white is repurposed as a hot traveler. In flexible cords and plugs, however, NFPA 70 (NEC) mandates white is always neutral. In IEC regions, blue is strictly neutral in cords. Never use a blue wire as a neutral in a US-manufactured appliance, and never use a white wire as neutral in an EU-manufactured appliance unless the cord is explicitly dual-rated and marked.
The UK Pre-2004 Legacy Trap
US 240V 3-Prong vs. 4-Prong Dryer/Range Plugs
Older US homes use 3-prong NEMA 10-30 or 10-50 receptacles for dryers and ranges. These cords have Black (Hot), Red (Hot), and White (Neutral/Ground bonded). Modern NEC code requires 4-prong NEMA 14-30 or 14-50 plugs, which separate the neutral (White) and ground (Green). If replacing a 3-prong cord with a 4-prong cord, you must remove the bonding strap inside the appliance terminal block to isolate the neutral from the chassis ground.
Decision Path: Selecting Your Replacement Cord and Standard
Stop guessing which cord to buy at the hardware store. Follow this decision tree to select the exact wire type, gauge, and plug configuration for your project.
| Scenario / Application | Required Standard | Concrete Pick (Buy This) |
|---|---|---|
| Replacing a standard US 120V appliance cord (lamps, routers, power tools up to 15A) | NEC (UL Listed) | 14 AWG SJTW 3-conductor cord with molded NEMA 5-15P plug (Black/White/Green). |
| Wiring an IEC C13/C14 inlet for a 230V desktop PC, server, or lab equipment | IEC 60446 | 3-core H05VV-F 1.5mm² cord (Brown/Blue/Green-Yellow) with IEC C13 connector. |
| Replacing a US 240V electric dryer cord (modern 4-slot outlet) | NEC (UL Listed) | 10 AWG 4-conductor NEMA 14-30P dryer cord (Black/Red/White/Green). |
| Wiring a high-draw US 240V EV charger or welder (50A) | NEC (UL Listed) | 6 AWG 3-conductor NEMA 6-50P cord (Black/Red/Green) — no neutral required for pure 240V loads. |
Safe Interpretation for Faded, Missing, or Non-Standard Cords
Imported electronics, cheap unbranded power supplies, and degraded vintage cords frequently violate standard color codes. You may open a plug and find red, yellow, and blue wires, or all three wires might be black with only faint printed ridges on the insulation to differentiate them.
The Rule: Never terminate a non-standard cord based on visual guessing. You must map the plug pins to the wire ends using a multimeter.
- Set your multimeter to continuity mode (the diode symbol that beeps when probes touch).
- Identify the plug pins physically. For a US NEMA 5-15P: the narrow flat blade is Hot, the wide flat blade is Neutral, and the U-shaped pin is Ground. For an IEC Schuko (CEE 7/4), the plug is unpolarized (Hot/Neutral can swap), but the metal grounding clips on the sides are Earth.
- Probe and map. Touch one probe to the Ground pin and the other to each wire end until you get a beep. Mark that wire as Ground (wrap it in green electrical tape). Next, probe the narrow Hot blade to find the Hot wire (mark with black tape). The remaining wire is Neutral.
If the cord is so degraded that the continuity test yields high resistance (>2 ohms) or intermittent beeps, the internal copper strands are fractured. Discard the cord; do not attempt to salvage it.
Terminal Pinout and Physical Wiring Verification
Knowing the wire plug color code is only half the job. Improper physical termination causes arc faults, melted plugs, and fires. Follow these bench rules when wiring your selected cord to a plug or appliance inlet.
Stranded Wire Termination Rules
- Never solder-tin the ends of stranded wires before placing them under a screw terminal. Solder creeps (cold flows) under mechanical pressure, causing the joint to loosen over time and create a high-resistance hotspot.
- Use ferrules for IEC inlets. When wiring European H05VV-F cords into IEC C13/C14 appliance inlets, strip the wire, apply a 0.75mm² or 1.5mm² bootlace ferrule, and crimp it with a proper ferrule crimper. This prevents stray copper strands from shorting against adjacent terminals.
- US NEMA screw terminals: If the replacement plug uses screw terminals instead of a molded strain-relief clamp, form a clockwise J-hook in the solid/stripped wire so that tightening the screw pulls the loop tighter, rather than pushing it out.
Strain Relief Verification
The ground wire must always be the longest wire inside the plug housing. If the cord is violently yanked, the strain relief should fail, then the hot and neutral wires should pull out of their terminals, and the ground wire should be the absolute last connection to break. This ensures that if a live wire shorts to the appliance chassis during a yank event, the chassis remains grounded long enough to trip the breaker. Always tug the cord firmly after assembly to verify the internal cord grip is clamping the outer jacket, not the individual colored conductors.
For further reading on international harmonization of wiring colors, refer to the IEC 60446 standard documentation and regional safety guidance from organizations like Electrical Safety First.
