ISO 24505-2:2025
(Main)Ergonomics — Accessible design — Part 2: Colour combinations for people with colour deficiency and low vision
Ergonomics — Accessible design — Part 2: Colour combinations for people with colour deficiency and low vision
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.
Ergonomie — Conception accessible — Partie 2: Combinaisons de couleurs pour les personnes atteintes de daltonisme et de malvoyance
General Information
Standards Content (Sample)
International
Standard
ISO 24505-2
First edition
Ergonomics — Accessible design —
2025-10
Part 2:
Colour combinations for people with
colour deficiency and low vision
Ergonomie — Conception accessible —
Partie 2: Combinaisons de couleurs pour les personnes atteintes
de daltonisme et de malvoyance
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 3
4.1 Application criteria for colour deficiency and low vision .3
4.2 Viewing modes and conditions .3
5 Colour combinations for people with protanopia and deuteranopia . 3
5.1 General .3
5.2 Protanopia .3
5.2.1 Two-colour combinations and their conspicuity for people with protanopia .3
5.2.2 Spans of fundamental colours of protanopia (Span 1) .4
5.3 Deuteranopia .6
5.3.1 Two-colour combinations and their conspicuity for people with deuteranopia .6
5.3.2 Spans of fundamental colours for deuteranopia (Span 1) .7
6 Colour combinations for people with low vision . 9
6.1 General .9
6.2 Two-colour combinations and their conspicuity for people with low vision .9
6.3 Spans of fundamental colours for people with low vision (Span 1). .10
7 Procedures to create a colour combination for people with colour deficiency and low
vision .12
Annex A (informative) Description and classification of colour deficiency, and sources of data
for the fundamental colour spans adopted in this document .13
Annex B (informative) Description of low vision and the sources of data for fundamental colour
spans adopted in this document .15
Annex C (informative) Textual descriptions of figures and tables for accessibility .18
Bibliography .27
iii
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
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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.
iv
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
[1]
order system recommended for use by the International Commission on Illumination.
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.
v
International Standard ISO 24505-2:2025(en)
Ergonomics — Accessible design —
Part 2:
Colour combinations for people with colour deficiency and
low vision
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
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 24505-1, Ergonomics — Accessible design — Method for creating colour combinations taking account age-
related changes in human colour vision
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 24505-1 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
anomalous trichromatism
form of trichromatism in which colour discrimination is less than normal
[SOURCE: CIE S 017:2020, 17-22-035, modified — Note 1 to entry has been deleted]
3.2
colour deficiency
anomaly of vision in which there is a reduced ability to discriminate between some or all colours
Note 1 to entry: Types of colour deficiency include:
— anomalous trichromatism: deuteranomaly, protanomaly and tritanomaly;
— dichromatism: deuteranopia, protanopia and tritanopia;
— monochromatism.
[SOURCE: CIE S 017:2020, 17-22-023, modified — "defective colour vision" has been changed to "colour
deficiency" and Note 2 to entry and Note 3 to entry have been deleted.]
3.3
deuteranomaly
anomalous trichromatic colour deficiency in which discrimination of the reddish and greenish contents of
colours is reduced, without any colours appearing abnormally dim
[SOURCE: CIE S 017:2020, 17-22-025, modified — "defective colour vision" has been changed to colour
deficiency, and Note 1 to entry has been deleted.]
3.4
deuteranopia
dichromatic defective colour vision in which discrimination of the reddish and greenish contents of colours
is absent, without any colours appearing abnormally dim
[SOURCE: CIE S 017:2020, 17-22-026, modified — "defective colour vision" has been changed to "colour
deficiency" and Note 1 to entry has been deleted.]
3.5
dichromatism
colour deficiency in which all colours can be matched using additive mixtures of only two matching stimuli
[SOURCE: CIE S 017:2020, 17-22-027, modified — "defective colour vision" has been changed to "colour
deficiency" and Note 1 to entry has been deleted.]
3.6
monochromatism
defective colo
...
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