Color and Aerial Perspective in the Sky

The sky itself, the lightest element in a picture, has different gradations, which causes variations in color and value from its highest point to the horizon. The reason for this is that the atmosphere for the sky at its highest point is the shortest distance with the clearest view. At the horizon, since the distance is longer, there are more “sheets” of atmospheric particles made up of gases between our eyes and the horizon. Like the colors of a rainbow, the zenith is a violet blue, as your eye turns toward the horizon, it changes to a truer blue, then a green-blue, a yellowish green, and finally a small strip of smoky warm rose nearest to the horizon, all the while lightening in value.  

An exception to this is sunrise and sunset, where the horizon takes on more oranges, reds, and purples because of the sun.

The above picture is an exaggeration of the color changes in the sky under sunny conditions.