Safety signs colours explained: UK guide

Red signs: prohibition and fire-fighting equipment

Red is used for two related but distinct purposes under BS EN ISO 7010, separated by shape:

Red circle with diagonal line on white = prohibition. The action shown in the pictogram is forbidden. Common examples include "no smoking" (lit cigarette with red diagonal), "no entry", "no naked flame", "no mobile phones", and "no running". The sign always uses a black pictogram on white inside the red circle.

Red square or rectangle = fire-fighting equipment. Marks the location of fire extinguishers, fire blankets, hose reels, fire alarm call points, and similar. The pictogram is white on the solid red background. These signs are always positioned directly above or beside the equipment.

The colour red was chosen because it is the colour with the strongest psychological "stop" / "danger" association across cultures. Both prohibition and fire-fighting equipment benefit from being recognisable instantly — fire equipment because it must be found in seconds during an emergency, prohibition because the brain processes "stop" signals fastest in red.

Blue signs: mandatory action

Blue safety signs tell you what you must do. They are always a solid blue circle with a white pictogram or short white text. Where you see a blue circle, an action is required. Common UK examples:

• Wear safety helmet (hard hat) — typically required on construction sites and at industrial entrances
• Wear hi-vis vest / clothing — required wherever workers and vehicles share space
• Wear safety footwear
• Wear ear protection — typically where noise exceeds 80 dB
• Wear eye protection
• Wear respiratory protection
• Fire door keep shut
• Keep clear (e.g. of fire exits, walkways, swing doors)
• Wash hands
• Use handrail

Mandatory signs are placed at the action point — at the entrance to the area where PPE is required, on the door that must stay shut, etc.

Yellow signs: warning

Yellow signs warn of a hazard. The triangle shape with a black border around a yellow background is one of the most universally recognised warning patterns — used in road signs, electrical labelling, and chemical hazard symbols. Pictograms are black on yellow.

Common UK warning signs:

• Slippery surface (also "wet floor" stand signs)
• Electrical hazard / risk of electric shock
• High voltage
• Flammable material
• Oxidising agent
• Toxic / poisonous material
• Corrosive substance
• Hot surface
• Forklift truck operating
• Deep water
• Falling rocks / falling objects
• Trip hazard

Warning signs are placed near the hazard, in line of sight before the hazard is reached. Where a hazard is permanent (e.g. high-voltage equipment) the sign is fixed to the equipment or its enclosure.

Green signs: safe condition

Green is the colour of "safe" — it identifies the option that gets people out of trouble. Green safety signs are always a green rectangle or square with a white pictogram. Common UK examples:

• Fire exit (running-man pictogram, with directional arrow)
• Emergency exit
• Escape route arrows
• Assembly point / muster point
• First aid
• First aid kit
• Eye wash station
• Emergency shower
• Defibrillator (AED)
• Refuge point (for evacuation in disabled access scenarios)

Green signs are placed along the escape route and at the equipment location. Fire exit signs go at every change of direction along an escape route, and above the final exit door.

Why the colour-and-shape system works

The combination of colour and shape is deliberately redundant. Even if a sign is partially obscured, faded, photographed in poor light, or seen by someone with colour vision deficiency, the shape carries the meaning:

• Triangle = warning, regardless of whether the colour reads as yellow or grey
• Circle with line = prohibition, even if the colour is hard to see
• Solid circle = mandatory
• Rectangle = safe condition or fire-fighting equipment

This is the same logic that drove road signs to use shape and colour together. It also means the system survives translation: a worker who can't read the English text on a "no smoking" sign still recognises the red circle with the diagonal line and the cigarette pictogram.

UK regulations behind the colour system

Three pieces of UK and European regulation set the colour and shape system:

• BS EN ISO 7010: the British/European/international standard that defines the precise colour, shape, and pictogram for every safety sign type. Updated periodically as new pictograms are added.
• Health and Safety (Safety Signs and Signals) Regulations 1996: the UK regulation that requires employers to display compliant signs where a risk cannot be avoided or sufficiently reduced by other means. Must be in colours and shapes that meet the standard.
• Regulatory Reform (Fire Safety) Order 2005: requires the responsible person to ensure adequate fire safety signage in non-domestic premises.

The colour system itself is older than the modern regulations — yellow-and-black warning, green-and-white "safe", and red-circle prohibition have been used in industrial settings since the early 20th century. BS EN ISO 7010 codified the de facto practice into a single international standard.

Browse signs by colour category

Every category in our shop is organised by the colour-and-shape system above:

• Red prohibition signs — no smoking, no entry, no naked flame, and similar
• Red fire-fighting equipment signs — extinguishers, hose reels, alarm call points
• Blue mandatory signs — PPE, hand washing, fire-door-keep-shut
• Yellow warning signs — slippery, electrical, flammable, hot surface
• Green safe condition signs — fire exits, first aid, assembly points