ABSTRACT
The metrical structure and dimensionality of color space were studied using estimates of large color differences. Multidimensional scaling of the data shows that the dimensionality of the space that provides a linear relationship between inter-point distances and chromatic differences is 4. However, color points do not completely fill in the four-dimensional space, but are located on a spherical surface. The perceived differences between colors are measured by Euclidean interpoint distances between points in the color space rather than by spherical distances. The phenomena of unique hue and color opponency were used to correlate the Cartesian axes with four ncurophysiological channels of color vision. Three spherical angles at each point on the sphere correspond exactly to hue, saturation, and brightness of spectral lights. The colors of monochromatic lights are represented by a curve on this sphere. The subset of equibright colors is located on the spherical surface in a three-dimensional subspace. The same results were obtained by reanalyzing Indow and Kanazawa’s (1960) data on color discrimination for Munsell colors. Functions are defined that relate Munsell color characteristics—hue, chroma, and value—with the three spherical angles of a color point in four-dimensional space.
