Aerial Perspective

Aerial Perspective is the change in appearance on items brought on by atmospheric conditions and its effect on color distinction, contrast, value, and hue. The atmosphere is made up of varying densities of gases composed of water particles that are perpetually suspended, similar to a mist. These gases act like slices of films rather than a solid body that collect in layers between our eyes and the distant horizon. The more slices of films between us and the horizon, the more it will affect the hue, contrast, and strength of the items in the distance.  It is said that all colors become cooler as they recede from the eye, except white.  Cooler means that colors take on more blue as the distance increases.
For blue to increase, some colors must decrease. The first hue to decrease is yellow. Yellow alone and in mixtures such as brown, green, and orange, decreases as the distance increase, while violets and blues increase in intensity. For very long distances, such as those found in the mountains and large open spaces of the western United States, after the loss of yellow, reds will then also decrease and blues will finally prevail. Along with the change of hues, all things will become lighter in value as they recede from the eye.  
What this means to an artist is that care should be taken to paint the nearer scenery darkest and most powerful in color and have more yellow and red, while items near the horizon should be painted in lighter values, and contain more blue, and less yellow, and desaturated reds. Edges should be softer, contrasts less distinctive. Whites, the exception, get warmer and darker as they recede.

This is my painting of Camden, Maine, from the park overlooking the harbor. The nearest trees were bright with autumn colors, but as the landscape recedes, the colors become lighter and the yellows start to disappear. The far horizon colors are purples and blues, devoid of all yellow.