Overview
ISO 22324:2022 - "Security and resilience - Emergency management - Guidelines for colour‑coded alert" provides international guidance on using colour-coded alerts to inform people at risk and first responders about hazard severity. Applicable to all hazards and locations, the standard clarifies colour meanings, ordering, supplementary codes and human-factor considerations to reduce confusion and prompt appropriate safety actions.
Key topics and technical requirements
- Primary colour meanings
- Red = danger - take safety action immediately
- Yellow = caution - prepare to take safety action
- Green = safe - no action required
- Supplementary colours
- Black / Purple = fatal danger (may be combined with red; checkerboard recommended on luminous displays)
- Blue = informational only (do not use to indicate hazard level)
- Grey = no information available
- Spectrum and ordering
- Use the red–yellow–green spectrum; if ordered visually, present increasing hazard left→right or bottom→top.
- Limit the number of levels (prefer minimal levels); use no more than seven colours to avoid confusion.
- Supplemental cues
- Always add supporting information (text, numbers, symbols, position or size) especially when more than three levels are used or when colour discrimination is limited.
- Human factors & accessibility
- Account for colour-blindness and viewing conditions; do not rely on colour alone for safety-critical decisions.
- Recommended text contrast for superimposed labels: white over black/purple/red/green; black over yellow.
- Colour specifications
- Annex B gives recommended hues in Munsell, CMYK and RGB systems for consistent implementation.
- Scope exclusions
- The standard does not cover display methods, detailed ergonomics of viewing displays, or safety sign formats covered by ISO 3864‑1.
Practical applications
ISO 22324 is designed for practical use in:
- Public warning systems and emergency management operations
- Early-warning dashboards, control rooms and digital alert displays
- Incident triage systems, maps (meteorological, radiological), and mass notification messages
- Emergency planning, training and communication templates
Benefits include clearer public warnings, reduced misinterpretation of alert levels, and improved cross‑agency consistency in colour-coded messaging.
Who should use this standard
- Emergency managers, public safety officials and civil protection agencies
- UX/UI designers for control-room and public-alert interfaces
- Authorities responsible for public warning, disaster communication and signage
- Vendors of alerting systems and digital signage
Related standards
- ISO 22322 - Public warning guidance
- ISO 22300 - Vocabulary (security and resilience)
- ISO 3864‑1 - Safety colours and safety signs (scope exclusion)
- ISO/TR 22411 and ISO 9241‑300 - Ergonomics and colour considerations
- ISO/IEC Guide 71 - Accessibility considerations for colour blindness
Keywords: ISO 22324, colour-coded alert, emergency management, public warning, hazard colour codes, red yellow green, accessibility, alert design.
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