When it comes to wiring, color coding is the common practice of assigning a particular color to each wire. Color coding is used in both industrial and domestic installations, and helps technicians understand the place and function that a specific wire has in a circuit. It offers a way for technicians to identify which wires are ground, hot, and neutral, ensuring safety and reducing maintenance time. National electrical systems follow color coding to comply with building regulations and maintain consistency. However, wiring colors may vary by region and country due to design standards. This comprehensive guide delves into the electrical wiring colors used worldwide.
The Purpose of Live, Neutral, and Earth Wires
A standard electrical cable transmits AC (alternating current) power. Standard electrical cables typically contain three wires:
- Live Wire: The live wire, line, or phase wire, carries the alternating current. It typically transports around 120 or 230VAC, depending on the region.
- Neutral Wire: The neutral wire completes the electrical circuit by offering a return path for the current to the source.
- Earth Wire: The earth wire, also known as the ground or protective earth wire, protects against electrical faults and helps to ensure the safety of the user and equipment. The earth wire provides a path for the current to safely discharge into the ground in the event of a fault.
Electrical Wiring Colors in the UK/EU
Most European countries follow the wire color code established by the International Electrotechnical Commission (IEC). This standard was originally published as IEC 60446 but was merged into IEC 60445 in 2010.
Current Wiring Color Code in EU: In 2006, an updated wiring system in the UK, ensuring that the UK’s wire colors matched those of other European Union member countries. This system followed the European harmonized wiring color scheme. The new wiring color codes for different supply systems in the UK/EU, as per IEC, are defined as:
Three-phase system: The preferred wiring color codes for a three-phase four-wire system are as follows:
- Phase 1 or Line, (L1) = Brown
- Phase 2 or Line 2, (L2) = Black
- Phase 3 or Line 3, (L3) = Gray
- Neutral (N) = Light Blue
- Protective Earth (PE) conductor = Green with Yellow stripe
Single-phase system: The following wiring color codes for a single-phase system are as follows:
- Phase or Line (L) = Brown
- Neutral (N) = Light Blue
- Protective Earth (PE) conductor = Green with Yellow stripe.
Previous Wiring Color Code in UK/EU: Before the standardization of wiring colors in 2006, the UK had an older color-coding system. Under this system, the line conductor was red, the neutral conductor was black, and the earth conductor was green with a yellow strip for single-phase supplies. In the old system, the wiring colors for three-phase systems are red, yellow, and blue for line conductors, black for neutral conductors, and green with a yellow strip for earth conductors in three-phase supplies.
| Function | UK (New Code as per IEC) | UK (Old Code) |
|---|---|---|
| Three Phase Line (L1) |  |
 |
| Three Phase Line (L2) |  |
 |
| Three Phase Line (L3) |  |
 |
| Neutral (N) | |
|
| Protective Earth or Gound (PE) |  |
|
| Single Phase Line | |
|
Figure 1: EU/UK Wiring color codes for AC (old and new)
DC wire color codes in EU/UK: Standard wiring color codes are used for two-wire grounded, two-wire ungrounded, and three-wire grounded DC power systems. These wiring color codes are adapted from IEC AC and applicable in the UK, EU, and other countries that follow the new IEC color codes.
Two-Wire Ungrounded
- Positive (L+) = Brown
- Negative (L-) = Grey
- Protective Earth (PE) conductor = Green with Yellow stripe
Two-Wire Grounded
- Positive (+ve) of Negative (-ve) grounded circuit (L+) = Brown
- Negative (-ve) of Negative (-ve) grounded circuit (M) = Blue
- Positive (+ve) of Positive (+ve) grounded circuit (M) = Blue
- Negative (-ve) of Positive (+ve) grounded circuit (L-) = Grey
- Protective Earth (PE) conductor = Green with Yellow stripe
Three-Wire Grounded
- Positive (L+) = Brown
- Mid-Wire as Center Tapped (N) = Blue
- Negative (L-) = Grey
- Protective Earth (PE) conductor = Green with Yellow stripe
| System | Function | UK (New Code as per IEC) | UK (Old Code) |
|---|---|---|---|
| Two Wire Ungrounded | Positive (L+) | |
|
| Negative(L-) | |
|
|
| Two Wire Grounded | +ve of -ve grounded circuit(L+) | |
|
| -ve of -ve grounded circuit(M) | |
 |
|
| +ve of +ve grounded circuit(M) | |
|
|
| -ve of -ve grounded circuit(L-) | |
|
|
| Three Wire Grounded | Positive (L+) | |
|
| Mid-Wire as Center Tapped(N) | |
|
|
| Negative(L-) |  |
|
|
| Protective Earth conductor | PE | |
  |
Figure 2: EU/UK Wiring color codes for DC (old and new)
Electrical Wiring Colors in the US
In the United States, the standard wiring color code for electrical installations is established by the National Electrical Code (NEC). The color codes for different AC and DC supplies are as follows:
120/208/240VAC: These systems are common in home and office environments, and can be identified by the following wiring color codes:
- Phase 1 or Line (L1) = Black
- Phase 2 or Line 2 (L2) = Red
- Phase 3 or Line 3 (L3) = Blue
- Neutral (N) = White
- Protective Earth (PE) conductor = Bare wire, Green or Green with Yellow stripe
In some wiring systems, the voltage in one phase will exceed the others. These are known as high-leg connections. This is common on a 240/120VAC 3-phase, 4-wire delta system, and is typically designated as “B phase.” According to NEC article 110.15, this high-leg wire should be marked with orange. It helps electricians test each phase, relative to the ground, to determine where the high leg is in the system. However, high-leg delta systems are typically not present in newer installations.
277/480VAC: Higher voltage systems are commonly used for industrial and high-power equipment such as motors, furnace, etc., and use the following color codes:
- Phase 1 or Line, (L1) = Brown
- Phase 2 or Line 2, (L2) = Orange
- Phase 3 or Line 3, (L3) = Yellow
- Neutral (N) = Grey
- Protective Earth (PE) conductor = Bare wire, Green or Green with Yellow stripe
| Function | Color Code (for 120/208/240VAC) | Color Code (for 277/280VAC) | |
|---|---|---|---|
| Three Phase Line (L1) | |
|
|
| Three Phase Line (L2) | |
 |
|
| Three Phase Line (L3) | |
|
|
| Neutral (N) | |
|
|
| Protective Earth or Gound (PE) |    |
||
| Single Phase Line |
|
||
Figure 3: US Wiring color codes for AC supplies
Wiring color codes for DC supplies in US: DC power is used in solar and battery power systems; they use the following standard wiring color codes:
- Positive (L+) = Red
- Negative (L-) = Black
- Ground = White or Grey
| Function | Color code for DC supply (US) |
|---|---|
| Positive (L+) | |
| Negative (L-) | |
| Ground | or |
Figure 4: US Wiring color codes for DC supply
Electrical Wiring Colors in Asia
In Asia, the various countries use their own standards and regulations for electrical wiring. There is no universal wiring color code for all of Asia. Wiring color codes can also vary significantly from one country to another. Here are some examples of wiring codes in Asian countries:
Electrical Wiring Colors in Japan: In Japan, 100VAC (Line to neutral) is used for single phase supply and Three Phase systems are 200VAC (Three lines, no neutral).
Single Phase AC supply: The preferred wiring color codes for single phase systems are as follows:
- Phase or Line(L) = Black or Red
- Neutral (N) = White
- Protective Earth (PE) conductor = Green
Three-Phase AC supply: The wiring color code for three-phase AC systems in Japan are as follows:
- Phase 1 or Line, (L1) = Black
- Phase 2 or Line 2, (L2) = Red
- Phase 3 or Line 3, (L3) = White
- Common Neutral (N) = White [Used in Two Lines System Only]
- Protective Earth (PE) conductor = Green
Figure 5: Wiring color codes for AC supply in Japan
Electrical Wiring Colors in China: The following wiring color codes are used in China for single-phase and three-phase AC supplies:
Single-Phase AC Supply: The preferred wiring color codes for a single-phase system are as follows:
- Phase or Line (L) = Yellow
- Neutral (N) = Light Blue or Black
- Protective Earth (PE) conductor = Green with Yellow stripe
Three-Phase AC supply: The wiring color code for three-phase AC systems in China are as follows:
- Phase 1 or Line, (L1) = Yellow
- Phase 2 or Line 2, (L2) = Green
- Phase 3 or Line 3, (L3) = Red
- Neutral (N)= Light Blue or Black
- Protective Earth (PE) conductor= Green with Yellow stripe
Figure 6: Wiring color codes for AC supply in China
Electrical Wiring Colors in India and Pakistan: India and Pakistan follow the legacy UK wiring color codes, and use red, yellow and blue for three-phase AC systems. In a single-phase AC supply, red is used for phase, while black is used to represent neutral.
