Why Are Swimming Pools Blue? 

Most of us probably agree that the perfect swimming pool should be blue; the bluer it gets, the better it looks. Whenever we see a pool of a different color, it tends to be unsettling and even repulsive as it implies that something is wrong with the water, and it just looks unsafe. This phenomenon often makes people wonder what causes this specific color and why we place so much importance on it. 

Swimming pools are blue mainly because of how the water interacts with light and the effects this produces. Water molecules absorb red light waves and reflect the blue ones, making the water appear blue. This visual effect may also be affected by the tile or surface colors and the color of the sky. 

In this article, I will explain in detail where the blue color of the swimming pool comes from, what causes it, and how we can enhance it. We’ll also try to see why this color is so important to us and why we emphasize it so much that it’s almost impossible to imagine pools in any different color. 

How Does Light Make Pool Water Blue?

light into pool makes blue

The interaction of light and water influences the perceived color of the water more than any other factor, and we can say that it is the sole reason for the color, while the other factors merely contribute to it. The process responsible for this is called electromagnetic absorption.

Light makes pool water blue when the blue waves get reflected from the surface of the water, while the red waves are completely absorbed. The green waves, on the other hand, become partially absorbed, causing some pool water to appear greenish-blue.

The shade of blue depends on the depth of the pool; the deeper it is, the bluer it is going to look. The same mechanism is in action whether it’s natural lighting or artificial – the results are the same. However, you can only see this in large bodies of water – which is why your glass or bottle of water looks transparent, even though it has the same white hue in it.

It’s also interesting to notice that the color of the water may vary based on where you are and what angle you’re at. The shade of blue that you see is not the same shade of blue other people will see, which makes this effect even more fascinating. 

The Composition of the Water

Another critical factor is what’s actually in the water. Different chemicals and different kinds of organic matter are going to have an effect on the composition of the water and thus on the way it interacts with light, which changes its color. 

The purer your water is, the bluer it will be, to put it bluntly. This may explain why we have a natural aversion towards pool water (and water in general) which isn’t blue. 

Algae and similar things can change the color of the water to a strange green color, which is usually a reliable indicator that the water is not safe to swim in. Unless, of course, you know that it was deliberately made green. 

Does the Sky Influence the Color?

A widespread and simple explanation for the color of swimming pools and large bodies of water, in general, is that it merely reflects the color of the sky. This should be a reasonable explanation, right? 

After all, the sky covers your outdoor pool, so, naturally, the transparent water will pick up the color. There could be a little bit of truth in this, but it is mostly wrong. 

The sky doesn’t influence the color of the pool water so much, although it reflects the sky to a certain degree. It merely adds to the blueness and affects the shade of blue, but it doesn’t cause it. If this were true, then indoor pools would probably not be blue. 

A bright summer sky will definitely make your pool stand out, and it will help bring out its blue color and make it look astonishing. However, your pool will still be blue even if the sky turns cloudy, although it will not look as nice.

How Tiles or Material Surfaces Make the Pool Water Blue

oval pool liner replacement

Another essential factor that will influence the color of your pool is your choice of tiles. Choosing a deeper shade of blue will make the blue of your pool deeper, while a lighter shade will make the pool water appear lighter. 

Your choice of tiles for an inground pool or the materials of your above-ground pool can be an excellent way to manipulate your swimming pool water’s color and achieve your desired aesthetic effect, but it still cannot make the water appear blue by itself.

They enhance and influence the color of the water, to a certain extent, which is why the right choice of tile color is crucial when buying or building a pool for yourself. 

Why People Prefer a Blue Swimming Pool

Blue is the most common color partly because we expect water to be blue, it feels like the most natural color for a pool, but also partly because we associate it with tranquility and serenity. After all, you probably want to get a pool to relax, and to do this, you want to enhance the feeling as much as possible, and likely to emulate the calmness of a sandy beach with a bright blue ocean. 

In addition, as mentioned before, many people feel uncomfortable when the water appears a different color. It becomes a bit uninviting. As a result, many resorts and hotels use the techniques mentioned above to manipulate the color of their pools. It further influences people’s belief that swimming pools should have blue water.


The reasons for the color of your pool are more complex than you might think at first, but it is possible to summarize them in four points. 

  • Light
  • Chemical composition
  • The sky
  • The color of tiles or materials

Light is the primary factor since the blue color is dictated by how water reflects and absorbs different colors in the spectrum. The color is further influenced by what’s in the water, the sky above, and the tiles you use for your pool. 


Recent Posts