We describe experiments on color mixing suitable for undergraduate nonscience majors. A commercial spectrophotometer is used to study the spectra of light sources, combinations of color filters, and mixtures of acrylic paints. Special emphasis is placed on teaching the fundamentals of subtractive color mixing and the complex processes that occur in mixing pigments.
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Definitions: Given any color, a matching color that appears to the normal retina identical to the color in question, can always be obtained by combining light of a single wavelength with white light (except for magentas and purples, which are specified by the complementary wavelength). The wavelength of the matching color is called the dominant wavelength. The corresponding attribute of visual sensation is called the hue. The fraction of white light is called saturation. Saturation is also known as purity. High saturation colors require a small percentage of white in the matching color, low saturation colors require a large percentage of white. These are pale pink, sky blue, pale yellow, beige, and all colors commonly called pastels. The adjectives saturated and pale are therefore antonyms. To match those colors, the matching color requires a large fraction of white. Some authors define saturation in paints and pigments to be the parameter related to the amount of black, but we do not see a reason for such distinction. Brightness (also known as lightness) is the parameter of a color according to which an area appears to emit more or less light. The adjectives bright and dark (or light and dark) are therefore antonyms. In the literature there is a preference to use the term brightness for luminant sources, and lightness for illuminated surfaces. Different color systems (Munsell, Oswald, and DIN) use other terms (for example, value, chroma), but for simplicity we use terminology familiar from everyday English.
