National foreword

This British Standard is the UK implementation of ISO 24505‑2:2025.

The UK participation in its preparation was entrusted to Technical Committee PH/9/-/1, Ergonomics of the physical environment.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October 2025.

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5, Ergonomics of the physical environment.

A list of all parts in the ISO 24505 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

Among people with visual disabilities, a considerably large number of people, especially male people due to a genetic reason, have colour deficiency of various types, and have difficulties identifying and discriminating colours in their daily life. A number of people also suffer from low visual abilities, and are clinically classified as having "low vision". These people can also have deteriorated colour vision and can experience confusion around some colours. As such, they can have problems with obtaining important public information such as warning signs and displays that use mainly colour to convey the message.

ISO 24505‑1 provides a method for creating conspicuous colour combinations that are discriminable or differentiated by people with no colour deficiency, but taking into account age-related changes in human colour vision with the aim of presenting better colour combinations to older people. Based on this methodology and basic colour vision data for people with visual disabilities, it is possible and required to establish a method to create colour combinations for people with colour deficiency and low vision to solve their problems in seeing coloured signs and displays.

Within this document, colours are consistently described using the Munsell Colour System. This is a colour order system recommended for use by the International Commission on Illumination.^[1^]

The selection of colours and their combinations for the specific use for safety conform to ISO 3864‑1.

This document adopts the guidance on accessibility presented in ISO/IEC Guide 71 and design guidelines presented in ISO/TR 22411.

This document is based on the method prescribed in ISO 24505‑1, but focuses specifically on data concerning fundamental colours for people with visual disabilities.

1 Scope

This document provides a method for creating conspicuous colour combinations for use in visual signs and displays in which multiple colours are used in various combinations to make them visible and conspicuous to people with colour deficiencies and low vision.

This document addresses protanopia and deuteranopia of dichromatic colour vision as typical cases of colour deficiency. This document does not cover tritanopia (another type of dichromatic colour vision) and anomalous trichromatic colour vision (protanomalous, deuteranomalous and tritanomalous) due to a lack of data.

This document covers low vision caused by various types of eye diseases, such as retinitis pigmentosa, macular degeneration, glaucoma, cataract, and others. It does not cover amblyopia, which also brings extremely low visual acuity but is classified differently in the medical field.

NOTE "Low vision" includes various types of permanent conditions of reduced visual abilities that cannot be rectified by optical refractive correction, and that are accompanied by extremely low visual acuity or limited visual field, central or peripheral.

This document applies to the reflective or object-mode of colours, but can apply to the self-luminous-mode of colours if their colour coordinates are appropriately transferred to those of the object-mode of colours.

2 Normative references

3 Terms and definitions

4 General

4.1 Application criteria for colour deficiency and low vision

4.2 Viewing modes and conditions

5 Colour combinations for people with protanopia and deuteranopia

5.1 General

5.2 Protanopia

5.3 Deuteranopia

6 Colour combinations for people with low vision

6.1 General

6.2 Two-colour combinations and their conspicuity for people with low vision

6.3 Spans of fundamental colours for people with low vision (Span 1).

7 Procedures to create a colour combination for people with colour deficiency and low vision

Bibliography

BS ISO 24505-2:2025

Ergonomics. Accessible design - Colour combinations for people with colour deficiency and low vision

Current

Published:

31 Oct 2025