In his studies, Rood established an important distinction between additive and subtractive colors. Additive colors involve light emitted from an illuminate source, and involve red, green and blue as primary colors. Combined together, these illuminated colors generates white light. Subtractive colors rely on three different primary colors, which are red, blue and yellow. The subtractive color model involves the mixing of paint or dyes, and is presently used in the process of printmaking or the creation of artwork reproductions.
Divisionist artists were attracted to Rood's work on the basis of his ideas regarding complementary colors. Complementary colors are any two colors that if united in the form of projected light will produce white light. Rood wrote that "an accurate knowledge of the nature and appearance of complementary colors is important for artistic purposes, since these colors furnish the strongest possible contrasts." Thus, when red is contrasted against blue, this combination of colors is exceptionally stimulating to the eye of a viewer and these colors appear to vibrate.
A consummate scientist in addition to being a theorist of art, Ogden Rood made repeated, specific measurements to understand and explain how color mixtures are formed from additive colors. He developed a system that showcases concentric color circles, which are broken into segments that contain numerous secondary colors that emerge from combinations of primary colors. These secondary colors include orange-yellow, green-yellow, green-blue, cyan and ultramarine-blue.
If you have ever tried to tune the colors on a television set or a computer monitor, you may be familiar with the concepts of hue, brightness and saturation. Such concepts were pioneered in Ogden Rood's color theory. He used similar terms to describe these same concepts: hue, luminosity and purity. These three terms comprise the "constants of color." Hue refers to a color's wavelength, and determine how closely it approximates the colors of a rainbow. Luminosity refers to the level of lightness or darkness present in a color. Purity describes a color's intensity, and essentially seeks to determine how much greyness the color contains.
Ogden Rood's color theory is crystallized in an influential work, "Modern Chromatics" (1879). Owned by both Georges Seurat and Paul Signac, both renowned Neo-Impressionist painters, this work distilled crucial ideas proposed by chemist Michel-Eugène Chevreul. Rood facilitates reader comprehension through careful, methodical explanation of complex concepts. Painters of the Impressionist movement were so inspired by Rood's observations that they began to reevaluate their painting techniques. Art critic Félix Fénéon dubbed this school of painters "the avante-garde of Impressionism", but later simply referred to them as the "Neo-Impressionists".