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Why are warning signs red, yellow, blue or green?

5th August 2014 | Health and Safety Signs

Everyone will have, at some point, seen a workplace safety sign. Green 'fire exit' signs are to be found in every public building, while any piece of remotely dangerous equipment will have a yellow or red warning erected somewhere nearby. These bold colours can cover some workplaces, such as factories and construction sites, where the risks are numerous.

However, while many people have seen these red, yellow, blue and green signs, few will know precisely why these specific colours are used. The same shades are in use on the vast majority of signs across the globe, with one or two exceptions, for the same purposes. Why are they so effective?

The answer is complex. Each colour has a different effect on people, sometimes unconsciously. They were not chosen at random either; the colours have been selected based on a number of factors that make each one the most suitable for safety signage.



Red was first used on road signs and traffic lights to indicate prohibitive dangers, or reasons to stop performing an action. You stop the car at a red traffic light, or stop travelling at 50 mph when you see a red sign indicating the limit is 30 mph. This has carried over into the workplace.

Red was first chosen because it is the most visible colour from a distance. The wavelength of red light is able to penetrate further through fog, dust and clouds, so you can see a red sign even in the dark or on a misty day. This was useful for road signs, as drivers needed to know about hazards a good amount of time before encountering them, so they could react accordingly.

Red has become associated with stopping in our minds because of this. In the workplace, this means you can see a red warning sign from far away and instinctively know to stop what you're doing and pay attention to it. This is why it is used for the highest levels of danger.



Once again, this is a very visible colour. One theory is that it is eye-grabbing because of its associations with the natural world. Bees and wasps around the world are yellow and black to signify how dangerous they are, warning predators to stay away, so yellow makes humans' unconscious minds take notice in case of a sting.

The colour's visibility combined with the feelings of danger it inspires make it perfect for the tier of danger below red. You can tell from a yellow sign that there is a potential hazard, but will notice the red signs first for immediate dangers.



Once again, driving provides a bit of an insight into why this colour is used. When you see blue while driving, it usually indicates a positive instruction; 'turn left ahead', for example, or 'one-way street'. These aren't warning of imminent dangers, just giving instructions to ensure a safer journey.

It is the same in the workplace. Blue does not elicit the same dramatic responses as 'danger' colours like red and yellow. It is fairly neutral in that respect. It is also one of the least visible colours from a distance. This makes it useful for positive instructions such as 'safety goggles must be worn' that are specific only to certain areas.

Essentially, blue is the colour used for non-urgent instructions, as it is a neutral shade that will not lessen the impact of the more important red and yellow signs.



This is essentially the 'safe' colour. Where red is the colour of blood and yellow the colour of stinging insects, green is the peaceful colour of plant life. On signs, it is used accordingly, as it typically shows you where places of safety are.

Green is used for fire exits and first-aid kits, for example, because in a moment of crisis our minds will latch onto the colour due to it symbolising life and therefore safety. This is one of the reasons it is used on traffic lights as well - where red and yellow are dramatic colours, green is calming so lets you know when it is safe to go.ADNFCR-2754-ID-801740148-ADNFCR


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