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 Each standard is tracked by authority, edition and status so a page cannot silently go out of date.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.

15 topics · 83 evidence-labelled claims · 63 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 where death or serious…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 an extinguisher made to the European standard EN 3 is red, whatever is inside, and the extinguishing agent is shown by…What happens to safety sign colours when the lights go out?They stop working as colours.Why is high-visibility clothing fluorescent yellow or orange?Because fluorescent yellow, orange-red and red are colours almost nothing in a natural or built background has, and a fluorescent…

Identification codes

Cables, pipes and indicators.

What do the colours of electrical wires mean?In the harmonised scheme used across Europe and in UK fixed wiring, which follows the IEC's rules for identifying conductors (IEC…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, a red indicator signals an emergency or hazardous condition needing immediate action…

Signals and navigation

Road signs, traffic signals, 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…What do the colours of road signs mean in different countries?Under the 1968 Vienna Convention, used across most of Europe, red borders warn and prohibit, blue grounds give mandatory instruct…

Accessibility standards

Contrast and colour-use requirements.

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