ISO 24505:2016

Overview

ISO 24505:2016 - Ergonomics: Accessible design - Method for creating colour combinations taking account of age-related changes in human colour vision - provides a standardized, evidence-based method to create conspicuous colour combinations for visual signs and displays that remain effective across age groups. The standard addresses how ageing and lighting (photopic and mesopic conditions) alter colour appearance and defines practical rules and data to select colours that are distinguishable to people of any age (excluding those with colour deficiencies or medical vision disorders). Keywords: ISO 24505:2016, ergonomics, accessible design, colour combinations, age-related colour vision.

Key Topics and Requirements

• Fundamental colours and spans: Defines 13 fundamental colours (red, orange/yellow-red, yellow, green-yellow, green, blue-green, blue, purple-blue, purple, red-purple, white, grey, black) and two span levels (Span 1 = highly similar; Span 2 = somewhat similar). Exact selections should come from Span 1 for each fundamental colour.
• Conspicuity classification: Colour combinations are classified as highly conspicuous, conspicuous, or slightly conspicuous based on geometric overlap of spans in colour space.
• Viewing conditions: Requires consideration of luminance level (photopic ~500 lx vs mesopic ~0.5 lx), ageing effects on colour appearance, viewing mode (reflective/object-mode vs self-luminous displays), field size (>20 minutes of arc), and surround (dark surround assumed).
• Tables and procedures: Provides experimental tables for two-colour combinations under four viewing conditions (younger/older × photopic/mesopic) and procedural steps to create multi-colour sets ensuring pairwise conspicuity.
• Scope limits: Not applicable to people with colour vision deficiencies or medical vision disorders. Primarily for reflective/object-mode colours; self-luminous colours are included only when appropriately converted.

Applications and Users

• Practical uses: design of safety and wayfinding signage, public displays, transport information panels, control-room displays, printed materials, and any multi-colour visual coding that must remain legible for older viewers.
• Who should use it: ergonomists, accessibility specialists, graphic and wayfinding designers, UI/UX and display engineers, transport and public infrastructure planners, safety sign manufacturers, and lighting designers concerned with colour appearance across age groups.
• Benefits: improves legibility and recognition for older users, supports accessible design requirements, and reduces misidentification caused by age-related colour changes.

Related Standards

• ISO 3864-1 - Graphical symbols - Safety colours and safety signs (normative reference in ISO 24505:2016).
• CIE documents (e.g., CIE S 017/E:2011) referenced for photopic/mesopic definitions.
• Annex C of ISO 24505:2016 gives guidance for transforming Munsell coordinates to CIE XYZ/sRGB for self-luminous displays.

For designs requiring accessibility across age groups, ISO 24505:2016 provides practical, standardized guidance on selecting conspicuous colour combinations under realistic lighting and viewing conditions.