There are four types of light sensitive cells in the retina: the rods and the S, M, and L cones (for, roughly, "short," "medium," and "long" wavelengths). These cells contain a molecule which changes shape when hit with a baseline level of photons, but each are sensitive to light waves of different wavelengths.
This process separates the highly correlated M and L cone signals in order to provide a richer color space. A consequence of the wiring from three wavelength detectors to two opponent color circuits is a circular color space, familiar to many as the color wheel. When we graph this color circle against the dimension of brightness, we get a spindle shaped space corresponding to the subjective perception of color.
Peter Gärdenfors has observed that if we consider the spindle shaped subspace of this color space which corresponds to possible human skin tones and attach our basic color words to the corresponding parts of this subspace, we can retrieve the use of these terms in describing human skin tone.
Here we have an example of a linguistic structure, an analogy, which is suggested, perhaps even forced, by the physiological structure of human perception. . . . and how many more also are?