Our perception of color is a by--product of visual perception. The world of electromagnetic stimuli in which we are immersed has a much more rich and varied structure than our visual system can process. We only perceive a limited range of frequencies of electromagnetic radiation, the narrow band of ``visible light'' which ranges in wavelength from approximately 360nm to 660nm. The visible wavelengths of light that are reflected from the objects in our everyday world are composed of mixtures of sometimes hundreds of separate and distinct frequencies of light. We somehow represent a distribution of frequencies of visible light as a single percept which we call a color. In doing so we have lost a great deal of the information that was originally present in light, in fact many different distributions of visible light can produce the same subjective color percept.
The difference between the objective physical nature of distributions of electromagnetic energy and our subjective perception of this energy caused a great deal of confusion for early researchers in optics. There is still much disagreement about the nature of the transformation from the spectral distributions of photic stimuli into our convincing and stable representations of a world in which color is a quality attached to every visible object. There is still no reliable ``uniform color metric'' which can accurately predict just noticeable differences across spectral distributions, illumination and contrast.
With that in mind, this paper retraces the history of color science, from the perspective of optical physics, psychophysics, mathematics and neurophysiology in order to gain a clear definition of the proper questions that need to be asked if we are to find a unifying framework for color perception.