Wiring color codes: An introductory guide to electrical wire identification

In both industrial and domestic applications, we see different colored wires such as red, yellow, blue (RYB) in a three-phase system and orange wires in electric or hybrid vehicles.

What does these colors signify? Is there any standard behind them? Our introductory guide will help you identify wires based on their colors and explain the meaning of each color code.

Why are wires assigned colors?

Assigning colour codes to wires is a global practice in industrial and domestic applications. It helps electricians place the correct wire in the circuit and ensures safety. Imagine the wiring harness in your car, which transfers signal and power to different components such as sensors, control modules, actuators are removed to carry out repair work. What would you do if there was no distinction between the three wires? A wrong placement may damage the components or cause a short circuit. Wire colors also indicate the amount of voltage carried by them. However, due to design standards, wiring colors may vary by region and country.

Role of live, neutral, and earth wires

A standard single-phase electrical cable that powers your home has three wires: phase(live), neutral, and earth. The live wire carries energy to the device, while the neutral sends back the current received from the power supply to complete the electrical circuit. The earth wire, or ground or protective earth wire, protects against electrical shocks by providing a path for the current to safely discharge into the ground in the event of a fault. There are also three-phase electrical cables, which you might have observed in motors powering the escalators in shopping malls or airports. There are generally four wires in a three-phase electrical cable: three for different phases and one for neutral.

Wiring colour codes for United Kingdom (UK) / European Union (EU)

The wiring colour code in the UK and most of the EU is governed by the IEC (International Electrotechnical Commission) standard. IEC published this standard originally as IEC 60446 in 2007. It provides general rules for the use of specific colors or alphanumeric markings to identify conductors, ensuring safety and preventing ambiguity. Later, IEC published different standards, like 60445:2010, for wiring colour, but those editions were withdrawn, and the latest standard is IEC 60445:2021 ed.7.

Wiring Color Code for AC system in EU/UK

As per the latest IEC standard, the wiring color codes used in single-phase and three-phase AC systems are used as follows:

1. Three-phase system: The recommended wiring color codes for a three-phase four-wire system are as follows:
   • Brown for Phase 1/Line 1
   • Black for Phase 2/Line 2
   • Gray for Phase 3/Line 3
   • Light Blue for Neutral
   • Green with yellow stripe for Protective Earth conductor
2. Single-phase system: In the UK/EU, the following wiring color code scheme is used for a single-phase system:
   • Brown for Phase/Line
   • Light Blue for Neutral
   • Green with yellow stripe for Protective Earth conductor

Old wiring color code in UK/EU

Although older cables are replaced with new ones once their life span ends, some old buildings across the UK still have cables with the previous colour scheme. So, it is equally important to be aware about the old wiring color code. Under this scheme, the line conductor was red, the neutral conductor was black, and the earth conductor was green with a yellow strip for single-phase systems. For three-phase systems, red, yellow, and blue were used for different line conductors, black for neutral conductors, and green with a yellow strip for earth conductors.

Figure 1: Wiring color codes for AC supply in UK/EU

Wiring color code for DC system in EU/UK

Like the AC system, the UK/EU follows standard wiring color codes for two-wire grounded, ungrounded, and three-wire grounded DC systems. These codes are adopted from IEC AC wiring color codes.

1. Two Wire Ungrounded
   • Brown for Positive(L+)
   • Grey for Negative(L-) and
   • Green with Yellow stripe for Protective Earth (PE) conductor
2. Two Wire Grounded
   • Brown for Positive (+ve) of Negative (-ve) grounded circuit(L+)
   • Blue for Negative (-ve) of Negative (-ve) grounded circuit(M)
   • Blue for Positive (+ve) of Positive (+ve) grounded circuit(M)
   • Grey for Negative (-ve) of Positive (+ve) grounded circuit(L-)
   • Green with Yellow stripe with Protective Earth (PE) conductor
3. Three Wire Grounded
   • Brown for Positive (L+)
   • Blue for Mid-Wire as Center Tapped (N)
   • Grey for Negative (L-)
   • Green with Yellow stripe for Protective Earth (PE) conductor

Figure 2: Wiring color codes for DC supply in UK/EU

Wiring color codes for the United States (US)

The United States follows the National Electrical Code (NEC) for wiring colors in electrical installations. It has separate color codes for different AC and DC supplies, which are as follows:

1. 120/240 Volt AC supply

   In the US, homes and offices are powered with 120V and 240V AC supplies. A 120V AC supply is used for lighting and plug loads, while 240-volt single-phase loads are used to power water heaters, electric ranges, or air conditioners. The individual colors assigned to different wires are:

   • Black for Phase 1/Line 1
   • Red for Phase 2/Line 2
   • Blue for Phase 3/Line 3
   • White for Neutral
   • Bare copper, Green or Green with Yellow stripe for Protective Earth conductor
2. 277/480 Volt AC

   In the US, commercial and industrial establishments are supplied with higher voltage of 277 / 480V three-phase power to power machinery such as motors, furnaces, etc. for which the color codes are:

   • Brown for Phase 1/Line 1
   • Orange for Phase 2/Line 2
   • Yellow for Phase 3 /Line 3
   • Grey for Neutral
   • Bare copper, Green or Green with Yellow stripe for Protective Earth (PE) conductor
   

   Figure 3: US Wiring color codes for AC supplies

3. Wiring color codes for DC supplies in the US

   DC power is popular in automotive and renewable energy applications like solar panels, electronic gadgets, etc. In the US, DC power uses red wire for the positive, black for the negative, and white or grey for the ground.

   

   Figure 4: US Wiring color codes for DC supply

Electrical wiring colors in Asia

In Asia, there is no universal wiring code for the entire continent. Different countries use their standards and regulations for electrical wiring. So, the wiring color codes vary from one country to another. Here are the wiring codes for some important Asian countries:

Electrical wiring colors in Japan

Japan uses 100V (Line to Neutral) for single-phase supply and 200V (three Lines, No Neutral) for three-phase supply.

1. Single Phase AC supply

   The wiring color codes for single phase system in Japan are:

   • Black or Red for Phase /Line
   • White for Neutral
   • Green for Protective Earth (PE) conductor
2. Three-Phase AC supply

   The wiring color code for three-phase AC supply in Japan are:

   • Black for Phase 1/ Line 1
   • Red for Phase 2 / Line 2
   • White for Phase 3 / Line 3
   • White [Used in Two Lines System Only] for Common Neutral
   • Green for Protective Earth (PE) conductor
   

   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:

1. Single Phase AC supply

   Wiring color codes for single phase system are:

   • Yellow for Phase/Line
   • Light Blue or Black for Neutral
   • Green with Yellow stripe for Protective Earth (PE) conductor
2. Three-Phase AC supply

   The wiring color codes for the three-phase AC supply in China are:

   • Yellow for Phase 1/Line 1
   • Green for Phase 2/ Line 2
   • Red for Phase 3 /Line 3
   • Light Blue or Black for Neutral
   • Green with Yellow stripe for Protective Earth (PE) conductor
   

   Figure 6: Wiring color codes for AC supply in China

Electrical wiring colors in India

India follows the IS 11353: 2023 standard for wiring color codes, which is given by the Bureau of Indian Standards and is based on IEC 60445: 2021. Table 1 shows the wiring color code schemes recommended for India.