Colour contrast diagrams from 'De la loi du contraste simultane des couleurs et de l'assortiment des objets colores' (The principles of harmony and contrast of colours) by the French chemist Michel Chevreul (1786-1889). These diagrams show how the perception of a colour changes depending upon its surrounding colours. This occurs because the brain exaggerates differences in hue and brightness, making juxtaposed colours appear more different than they actually are. This phenomenon is known as simultaneous contrast. These dots are arranged to produce harmonies of contrast against the black background.