Analysis: The decision to wear red was influenced by other gift-bringers, but there is also a scientific reason for Santa's red outfit

By Barry Fitzgerald, Eindhoven University of Technology

You've probably heard the story before – Santa Claus wears red because of Coca Cola. Well, that’s just not correct – and Cola Cola will tell you that themselves too. The truth is that Santa Claus was inspired to wear red by other gift-bringers from around the world.

First to inspire Santa’s choice of red was Saint Nicholas, a kind-hearted individual who gave gifts to the poor while wearing red robes when he worked as a bishop in the 4th century. Second to divert Santa’s attention to the glory of red was the Dutch gift-bringer Sinterklaas, who delivers presents on the evening of December 5th each year. Sinterklaas does it all in red too.

From The History Channel, the evolution of Santa Claus

So, Santa Claus’ decision to wear red was influenced by the success of other gift-bringers, and not by a marketing campaign from a soft drinks manufacturer. Nevertheless, there is also a scientific reason as to why Santa Claus wears red – and it all comes down to not being seen on Christmas Eve.

Hold on for a minute. When anyone wears red, it’s easy to see that they are wearing red. So, why would Santa opt for a colour that’s seemingly so easy to see? To explain Santa’s choice and how red helps him go about his business unnoticed on Christmas Eve, let’s explore how your eye sees colour.

Eyes are windows to a colourful world

The old saying goes that "the eyes are the windows to the soul". However, they’re much more than that – they’re the portals that allow us to perceive the beauty of the world. And part of that beauty is colour. When light enters your eye it’s focused by the cornea and lens at the front of the eye onto the retina at the back of the eye.

From TED-Ed, educator Colm Kelleher on how we see colour

At the retina, the light interacts with so-called photoreceptor cells. These cells just love to interact with light and create chemical and electrical impulses when they do so. Without getting into all of the biological details, this produces signals that are sent through the optic nerve into the brain where the brain unravels the signals to create an image of what’s in front of your eyes.

Rods and cones

Let’s backtrack a little though because the retina of anyone’s eyes (including Santa Claus too) contains two important types of photoreceptor cells – rods and cones.

Rods are your friends when it comes to seeing things in the absence of bright lights. In other words, they’re great at helping you to see in the dark. This sounds like a contradiction, but you can see a little bit in the dark, and its thanks to rods.

On the other hand, cones do their best work when it’s bright. Added to that, they help you see colour, and there are three different types of cones, each sensitive to a different colour – red, green, and blue.

Hiding in red

But where’s the connection with Santa Claus’ red suit then? Well, when the sun sets and day gives way to night, the amount of light around is not what it used to be. We all know that, Santa Claus knows this too and he knows that your eyes start to feel the effect, especially when it comes to seeing red.

In darkened conditions, it turns out that red light is the colour that the human eye finds hardest to see. In fact, red objects tend to look darker and bluer than other coloured objects. If Santa Claus wore blue, we’d have a much easier job of spotting him at night during his round-the-world trip.

If you’re a cinema fan, you’ve experienced this effect of not being able to see red in dim conditions before. In cinemas, red is the colour of choice for the comfy seats. This means that when the lights go down, the seats become darker and it’s harder to see their exact colour. If the seats were blue or green, those colours would be easier to see than red, and that might distract you from whatever you are watching in the cinema.

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Santa’s red invisibility cloak

With this knowledge on how your eyes work, Santa wears as much red as he can. In fact, it would be best if his suit were all red, and the sleigh too for that matter. Added to that, the reindeers’ natural fur coats tend to be brown, which contains quite a bit of red too. This also makes it difficult for you to see the reindeer.

In the end, Santa Claus doesn’t need an actual invisibility cloak, although there can be no doubt that he’s got one of those too! What matters here is that Santa Claus dons his red suit on Christmas Eve for one big reason – his red suit (and red sleigh and brown reindeer) will be harder to see as they glide across the background of a darkened sky.

Santa is just taking advantage of how your eye works and processes light to see colours. He’s using science against you, and for good reason. Wearing red aids his efforts to circumnavigate the world in stealth mode with the intention of delivering presents to you and yours under the cover of darkness. Throw the 'Coca Cola and Santa Claus wearing red’ story in the bin. Instead, it can be traced back to science and how your eyes distinguish the colours around you.

Best of luck Santa Claus with your trip this year! You got this! And don’t forget – keep it red.

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Dr Barry Fitzgerald is a science communicator at Eindhoven University of Technology in the Netherlands, and adjunct associate professor at UCD. He is the author of Secret Science of Santa Claus and does research on the science behind Santa's incredible Christmas Eve journey.