Why Sirens Use Red and Blue Lights

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Written By Cecilia Camille

I'm a mother of four and a writer who loves to blog, write, and be involved in online communities. I have experience with parenting as well as technology-related work. In fact, I've always been interested in how technology impacts the world around us.

Ever wondered why most sirens use red and blue lights?

The siren is one of the most ancient and widespread emergency signals. The red and blue lights on top of a police car or fire truck are a beacon for help, but why do these colors signify that there is danger?

The answer, as it turns out, is rooted in ancient mythology. In the 1930s, when vehicle-based sirens began being used to relay critical information quickly in an emergency, they were historically painted red with white stripes to differentiate them from other vehicles around them.

Following the development of red and blue lights that could be mounted to the top of a vehicle, these colors proved to be far more potent than anticipated. According to Vox, when an emergency vehicle with red and blue lights behind it passes you, you are likely to experience a startle response, in which your heart rate jumps and blood pressure rises. Your senses become heightened — even if you are not directly in the path of danger. This happens because the brain processes the combination of a potentially dangerous object moving in your direction and its color, which are signs of danger as far back as our evolutionary history.

It’s also been observed that when you see this color combination, you may be more likely to reach for your cell phone to report something about it, whether you have witnessed an emergency or not. This indicates that people are unconsciously aware that something is amiss when they see those two colors.

The colors are also present in nature, perhaps most visibly in the colors typically used by venomous snakes and poisonous or dangerous animals, such as spiders and frogs. The red is striking on a black or brown animal, while the blue is similarly bold on yellow or orange. Catching the attention of humans is imperative if a creature wants to avoid being killed by us.

The color combinations used to signify danger are also present in some cultures’ flags. The blue and white stripes on American flags are commonly used to represent peace, while the red symbolizes the bloodshed for the freedom of America. This is still true in many countries today, as evidenced by present-day Italian flags and their use of a red square with a white cross on it.

Red, blue, and white are also used to indicate danger or authority. Cars often have sirens and lights shaped like eyes to catch potential criminals’ attention better. Police officers, firefighters, and other emergency personnel often wear clothing with these colors to indicate that they are authorities. In the case of firefighters, this dates back to the 1500s, when firefighting was a much more dangerous job, and it was easier for firefighters to get the attention of people in a burning building if they were wearing bright red.

So when you see these colors together or in combination with each other, your brain’s danger warning system is activated immediately. They are both a signal of danger and a sign of authority, which prepare you for action.