http://en.wikipedia.org/wiki/Stanley_McCandless
McCandless Method
The McCandless Method is a particular approach to providing stage lighting, first proposed in his book, A Method of Lighting the Stage, which has been through several editions. The McCandless Method is still in wide use today.[1]
In the McCandless Method, the actors are meant to be fully front lit but also provided with some “sculpting” of the features. Full lighting is provided by at least two lights from opposite sides, above the plane of the actors by about 45 degrees and approximately 90 degrees apart. These two lights come in from opposite directions. Top lighting may also be used for fill, as may limited footlights. McCandless described these angles as being the diagonals of a cube in the center of the acting area.
However, the key to the McCandless Method is that one light of the primary pair is “cool” relative to the other. One may be blue (a cool color) and the other amber (a warm color). Thus, one fills the shadows left by the other in a way that produces a degree of depth uncommon in real life but striking and recognizable on the stage, similar to stage makeup in the way it exaggerates and clarifies the actors’ faces. Stanley McCandless developed the method in part while at Harvard College before he moved to Yale University, which was at the time near the center of American Theatre, in part because it was where many shows bound for Broadway, New York, opened and had initial runs, to judge their future potential.