ISO 24505-1:2025

Overview

ISO 24505-1:2025 - "Ergonomics - Accessible design - Part 1: Colour combinations for young and older people without visual impairments" provides a standardized method to create conspicuous colour combinations for visual signs and displays that account for age-related changes in colour perception. Based on perceived colour similarity under photopic and mesopic lighting, the standard uses the Munsell colour system to define 13 fundamental colours and their perceptual spans (Span 1 and Span 2). It applies to reflective/object-mode colours and can be extended to self-luminous displays when appropriate coordinate conversion is applied.

Key Topics

• Scope & limitations
  • Applies to people with normal colour vision across ages; not intended for people with colour deficiencies or medical vision disorders.
  • Primarily for object-mode colours; self-luminous conversion guidance provided in Annex C.
• Fundamental colours and spans
  • Thirteen fundamental colours (e.g., red, yellow, green, blue, purple, white, grey, black).
  • Span 1 (high similarity) and Span 2 (broader similarity) define acceptable ranges in colour space.
• Conspicuity classification
  • Three levels: highly conspicuous, conspicuous, and slightly conspicuous, determined by overlaps of Span 1 / Span 2 in colour space.
• Factors affecting conspicuity
  • Luminance level (photopic vs mesopic): colour appearance changes with light level.
  • Ageing effect: older viewers perceive some colours differently (e.g., bluish tones may be harder to distinguish).
  • Viewing mode & conditions: surround, field size (>20 minutes of arc), and illumination spectrum (document based on daylight fluorescent) influence appearance.
• Practical procedures
  • Clause 6 provides procedures to create colour combinations; Annex A, B and C include spans, an applied colouring example (train network) and transformation guidance to CIE XYZ / sRGB.

Applications

ISO 24505-1:2025 is valuable for professionals designing visual information where age-inclusive colour conspicuity matters:

• Signage and wayfinding (transport hubs, public buildings, healthcare facilities)
• User interfaces and displays (industrial control panels, kiosks, public digital signage when colour conversion is managed)
• Product and packaging design requiring clear multi-colour differentiation for mixed-age audiences
• Ergonomics and accessibility consultants, UI/UX designers, facility managers, transportation authorities, and safety communicators

Note: For safety-critical colour use, follow ISO 3864-1 in conjunction with this standard.

Related standards

• ISO 3864-1 - Graphical symbols - Safety colours and safety signs
• ISO 24505-2 / ISO 24505-3 - companion parts referenced in the series

Keywords: ISO 24505-1:2025, ergonomics, accessible design, colour combinations, older people, photopic, mesopic, conspicuity, Munsell colour system, visual signs, displays.