Joseph Albers' Color Theory

The little green boxes in the middle of the image are the exact same color. Hard to believe isn't it, but it is true. Joseph Albers was a genius that taught about perception and observation and how to really see the truth of our environments.
Painter, sculptor, and architect Josef Albers (American/German, 1888–1976) taught at the Bauhaus, one of the most prestigious and progressive art schools in Europe, and is considered one of the most influential art teachers of the 20th century.  In 1963, Albers published a treatise on color theory, entitled The Interaction of Color, and his experiments with color and geometric abstractions led to further series, including Variants, Biconjugates, Structural Constellations, and sandblasted glass paintings. The below quote is from Josef Albers' text The Interaction of Color. Albers describes his approach to teaching color theory.

“In visual perception a color is almost never seen as it really is- as it physically is. This fact makes color the most relative medium in art.”

“In order to use color effectively it is necessary to recognize that color deceives continually. To this end the beginning is not a study of color systems.”

First, it should be learned that one and the same color evokes innumerable readings. Instead of mechanically applying or merely implying laws and rules of color harmony, distinct color effects are produced- through recognition of the interaction of color- by making for instance 2 very different colors look alike, or nearly alike.  Albers was very interested in the relationships of color. His work can be thought of as the "Yin & Yang" of color theory. In that all color is read in relation to other color. You cannot have warm without cool.