Aquatic Technology Pool & Spa

Beyond Basic Blue: Using Color Theory

Beyond Basic Blue: Using Color Theory

By Paolo Benedetti

Beyond Basic Blue: Using Color TheoryEven though most people think it's simple, working with color in the presence of water is surprisingly complex. This is why I find myself calling up my patience when a client says, "I want the pool finish to be blue so that the water will look blue" - I know I'll have a lot of explaining to do.

What most people (including, it seems, a lot of people in the watershaping field) don't understand is that a myriad of variables and principles are involved in determining what color water appears to be.

While there is some relationship between the interior surface color and the appearance of the water, a range of factors affect the perceived color of the water in a swimming pool, fountain or spa. This is why working with the client's request for a blue interior finish is no guarantee that the pool will appear blue once the vessel is filled with water.


Topping the list of these factors is the way optical physics inevitably works in water.

Basically, water is clear rather than tinted (at least, if the water is clean). When placed in a pool or fountain, it does not assume the color of its surroundings, as though it were a chameleon; instead, because of the applicable physics, water has some interesting interactions with light, bending it in a phenomenon known as refraction.

This is why, when you stand on the side of a pool and look at underwater objects, those objects aren't quite where they appear to be. If you doubt that, take a long stick and poke a length of it beneath the surface: It will appear to bend just below the waterline.

This happens because light travels more slowly in water than it does in air; as a result, not only do objects appear bent, they also appear larger than they really are. And because light is scattered as it passes through water, the deeper you go the less contrast objects will have - which is why objects lying on the bottom of a 20-foot-deep pool seem washed out visually.

And there's more: Light is also absorbed as it passes through water and dissipates rather quickly. This is why, in two holes of equal depth - one empty, the other filled with water - the hole with the water in it will be darker at the bottom. (Scuba divers know these optical tricks far better than people who work with eight-foot-deep watershapes, but all the same principles apply.) As a byproduct of this process, various colors of the light spectrum are absorbed by the water at different rates. Some colors are not as intense and are absorbed rather quickly, while others are able to penetrate deep into the water.

This process of absorption has the greatest effect on the colors we think we see underwater - that is, the perceived color. Red, for example, is the least-intense color on the spectrum and is filtered out at rather shallow depths. Orange is next, followed by yellow, green and then blue. A deep, clean body of water will therefore appear blue when viewed from the proper distance and angle.


So how do we predict what color a viewer will perceive? We use basic color theory.

Shallow water does not have much of a filtering effect on red and orange light, which explains why a pool appears to be bluer in the deep end than in the shallow end: The red light is filtered out and the blue light passes through to the bottom of the pool.

It is this surviving blue light that reflects back to the eyes of the person standing beside the pool - but the blue light comes along with the color of the pool's finish, so things can get a bit complicated.

For example, if the pool has a tan or brown pebble finish (that is, something in the yellow part of the spectrum), the water in the deep end of the pool will look green (yellow + blue = green). By contrast, if the pool has a red finish, the water will look red in the shallow end but will appear violet in the deep end (red + blue = violet).

But that's not where it ends, because there are several other real-world factors at play here, including:

>> Sky: If the sky is bright blue, that color will be transmitted to the pool. If the sky is cloudy or a sunset orange, those colors will be transmitted into the water as well. So a pool at sunset overlooking the ocean will appear much different than a pool in the snow-covered mountains on a cloudy day.

>> Viewing Angle: Imagine looking down on a pool from the tenth floor of a hotel. The viewer takes in the entire scene - both deep and shallow ends at once - unaffected by any glare or reflected light. The closer the viewer gets to the water - down, say on the second floor - the more glare and reflected light come into play to dramatically change the perception of refraction and the combinations of color formerly perceived from on high.

>> Proximity: If the viewer comes close to the pool's edge, the perceived colors are different than they will be if perceived from the tenth or even the second floor. Moreover, at close range our eyes automatically focus and try to see the bottom of the pool, so we don't as effectively absorb the colors that are presented. In other words, the greater the distance from the pool, the easier it is to focus on the overall scene rather than the details. A bit of distance improves our ability to observe the blending of light and materials and affects the way we perceive colors.

>> Environment: Objects in the immediate vicinity of a swimming pool also contribute color to the water. Tall buildings, trees, shrubs, retaining walls and decking all lend their colors to the setting and the water. Indeed, any item reflected on the surface of the pool changes our perception of the pool's color.


There's no shortcut to experience when it comes to manipulating color in an aquatic environment. If it is important to you (or, more significant, to your client) to achieve a certain color, then it is best to hire someone who has had some training in color theory and who knows how to manipulate perceptions to achieve desired results.

If that seems extreme, just roll through the above list a factors, recognize how many of them are in constant states of flux and accept the fact that this is really more an art than a science. If you don't have the expertise your clients require of you, it's time to find someone who does. After all, we work in a visual medium - which is why I place an understanding of how color works very near the top of my list when it comes to getting educated.