Colour Standards

The colours that are specified rather than chosen: safety signs, pipe and cable identification, signal lights, navigation lights and accessibility requirements. Each standard is tracked by authority, edition and status so a page cannot silently go out of date.

Standards are summarised in Colourwise's own words. Their text, tables and diagrams are copyright and are not reproduced; each page says where to obtain the authoritative edition. Nothing here is legal or compliance advice.

12 topics · 51 evidence-labelled claims · 29 sources

Safety signs and marking

Warning, prohibition, mandatory and safe-condition colours.

What do the colours on ISO safety signs mean?Under ISO 3864-1, red means prohibition (and marks fire equipment), yellow warns of a hazard, blue orders a specific action and g…What is the difference between DANGER, WARNING and CAUTION colours on US safety signs?In the American ANSI Z535 system the colour of the header panel encodes how bad the hazard is: red DANGER for a hazard that will…What does EU safety-signs law say about safety colours at work?Directive 92/58/EEC, implemented in Great Britain by the 1996 Safety Signs and Signals Regulations, makes four colours carry fixe…What do the colours on fire extinguishers mean?In the UK and the rest of Europe an extinguisher is red all over, because EN 3 requires fire equipment to be red; the extinguishi…

Identification codes

Cables, pipes and indicators.

What do the colours of electrical wires mean?Under the international scheme in IEC 60445, now used across Europe and in UK fixed wiring, green-and-yellow is only ever the pro…What do pipe colour codes mean?Pipe colours tell you what is inside, but the UK and US systems ask different questions.What do gas cylinder colours mean?In Europe and the UK, EN 1089-3 colours the shoulder of a gas cylinder — the curved top — by the gas's main hazard: yellow for to…What do the colours of machine indicator lights and push-buttons mean?On industrial machines built to IEC 60204-1 and the coding principles of IEC 60073, red signals an emergency or fault and is used…

Signals and navigation

Traffic, aviation and marine lights.

Why are traffic lights red, amber and green?Traffic lights inherited red for stop and green for go from railway signalling, and added an intermediate amber (called yellow in…What do the coloured lights on aircraft and at airports mean?An aircraft shows a red light on its left wingtip, green on its right and white at the tail, so another pilot can tell which way…Why do ships show a red light on the left and green on the right?Under the international collision regulations (COLREGs), a vessel shows a red sidelight on its port (left) side and a green one o…

Accessibility standards

Contrast and colour-use requirements.

What does WCAG 2.2 require for colour and contrast?WCAG 2.