Pairs of colors seen to be in strong contrast to one another. This is achieved through the strengthening of a secondary (i.e. mixed) color (for example green) when it is placed opposite the primary color (in this instance red) that is adjacently positioned in the color circle next to the two primaries (blue and yellow) which together make up that secondary color. Similarly, blue strengthens orange and yellow strengthens violet. The optical interaction of colors in this manner was explored in particular by the chemist Michel-Eugène Chevreul who was appointed Director of Dyeing at the Gobelins tapestry workshops in 1824.
He published his chromatic circle of colors in 1839. The findings of Chevreul, and also of the aesthetician Charles Blanc, the latter first published in 1866, were highly influential on the Impressionists and, to an even greater degree, on Georges Seurat (1859–91). His pseudo-scientific system of using dots of pure color relied on the ‘blending’ of these separate colors by the eye, resulting in a vibrancy of color in his work unmatched by previous artists.