IEC 60757:2021

Overview

IEC 60757:2021 is an international standard developed by the International Electrotechnical Commission (IEC) that establishes a code for the designation of colours in electrical installations, equipment, and products. This standard specifies letter codes representing colours and rules for combining these codes to describe colour combinations. Primarily intended as a basic safety publication, IEC 60757:2021 supports technical committees in developing safety-related documentation and markings following IEC Guide 104 and ISO/IEC Guide 51 principles.

This second edition, a technical revision of the 1983 original, streamlines the colour coding system by restricting it to letter codes, adds information on alternating colours, and provides RGB encoding examples for clarity. It is important to note that this standard is not intended for manufacturers or certification bodies and does not specify the visual representation or physical colour properties encoding, which fall under individual technical committees’ responsibilities.

Key Topics

• Letter Codes for Colours
  IEC 60757:2021 assigns unique two-letter codes to colours commonly used in electrical documentation and equipment marking, including black (BK), brown (BN), red (RD), green (GN), and blue (BU), among others. For instance, black is designated as BK, while green is GN.

• Combination Rules for Colour Designations
  The standard provides clear rules on how to combine individual letter codes to represent multiple colours:

  • When multiple colours are present on the same item, codes are concatenated in a predefined sequence (e.g., red and blue combined as RDBU).
  • Alternating colours on one item use letter codes separated by a slash, for example BU/WH for an LED alternating between blue and white.
  • For subitems with different colours within an item, codes are joined by a plus sign, such as BK+BN+GNYE+BU+GY for a cable with cores of black, brown, green-and-yellow, blue, and grey.

• Special Combinations and Restrictions
  The green and yellow combination (GNYE) is restricted to specific uses aligned with IEC 60445, reinforcing safety standards in electrical wiring.

• Annex A – RGB Encoding Samples
  Provides visual guidance with RGB codes (e.g., Red: 255;0;0, Blue: 0;0;255) to ensure unambiguous colour identification without enforcing colour matching or representation requirements.

Applications

IEC 60757:2021 is crucial for standardizing colour designation in technical documentation and marking across the electrical sector. Its practical applications include:

• Electrical Installation Documentation
  Ensures consistent and internationally understood colour coding for wiring diagrams, schematics, and product manuals.

• Marking of Electrical Equipment and Products
  Provides standardised colour codes for labels, terminals, and conductor identifications to enhance safety and reduce errors in installation and maintenance.

• Development of Safety Publications
  Assists technical committees in creating safety-related standards where colour coding is essential for compliance and user protection.

By adopting IEC 60757:2021, stakeholders in electrical engineering can ensure clear communication about colour-coded elements, improve safety, and align with international standards.

Related Standards

• IEC 60445 – Basic and Safety Principles for Man-Machine Interface, Marking and Identification
  IEC 60757 references IEC 60445 specifically for restrictions on the use of the green-and-yellow combination indicating protective conductors.

• IEC Guide 104 and ISO/IEC Guide 51
  These guides provide principles for preparing basic safety publications, under which IEC 60757 is categorized.

• Other IEC Technical Committee Publications
  Responsible for visual representation and physical encoding of colour properties, complementing the designation codes of IEC 60757.

Keywords: IEC 60757:2021, colour designation code, electrical installations, electrical equipment marking, IEC colour coding, letter codes for colours, safety standards, electrical wiring colour code, RGB colour encoding, IEC electrical standards.