Measurements of the color of natural and restorative craniofacial and dental materials have many important applications to clinical practice and research. Although the specification of color at the level of the human observer involves only three dimensions or a color difference between two colors, a more technical viewpoint of color determination involves the visible spectrum. This review will provide the link between the spectral, the three-dimensional and the color difference aspects of color and emphasize important geometrical aspects of all measuring systems. Further, evaluations of accuracy and precision of measuring systems and considerations of acceptability and perceptibility of a color difference are reviewed, and applications of color measurements to important appearance characteristics of natural and restorative materials are briefly introduced.