The concept of “simultaneous contrast” refers to a phenomenon in which our eye is the perception of any color immediately require the appearance of his complementary color, and if that is not present, the simultaneous, ie at the same time, it generates it himself. This fact means that the basic law of color harmony is based on the law of complementary colors. Generated by simultaneous colors appear only as a feeling and not objectively exist. They can not be photographed. Simultannyi contrast as serial contrast, likely occur on the same reason. You can put the following experience: a large, brightly colored plane to place a small black square and then put it on top of a piece of tissue paper. If this plane is painted in red, the black box will appear greenish, if green, the black box will appear reddish to purple background – yellow, but if you put it in the yellow, the black box will appear purple and gray. Each color in the eyes of the viewer at the same time gives rise to its opposite tone.
Figures 31 … 36 show this experience in a different way. In each of the six squares painted in pure colors, placed at a small square of neutral gray color, which corresponds to the lightness of the primary colors brightness. And as soon as each of those gray squares begins to acquire an additional shade of color to the basic tone of the large main square. Through this experience, and observing the change in shade of gray in some colored square should be warned that all other boxes must be covered, and the sheet on which they are located close to the eyes. Simultaneous action will be the stronger, the more we look at the basic color and brighter than his tone. Since the simultaneous arising of color do not really exist, and appear only in the eyes, they evoke in us a sense of excitement and a living vibration of continuously varying the intensity of the color sensations. Prolonged viewing the basic color as it loses its power, the eyes get tired.