Physics can measure color: its energy and the length of waves are measurable. Color influences us on psychological level, and certain reactions to color can be measured. Physiological responses, like for example increase of blood pressure in reaction to red, or increased appetite in reaction to orange, and other reactions to other colors are measurable also. This belongs to the domain of psychologists and other researchers in the medical field.
There is of course the realm of emotional responses to color, which are individual, but quite often also culturally influenced. But what about art history? Do we can better understand art if we know more about color? Or is color only a part of a given artist's aesthetic preferences, matter of subjective, personal taste?
Yes, we can understand more about art if we know more about color. Any color palette of a given epoch was also reflection not only of tastes, but also the philosophy and theology of the times, as or example in Medieval art. But color choices also depended on very mundane matters, such as the accessibility or shortage of certain pigments.
Color as simply a matter of artistic tastes of creative individuals and nothing more? Yes, very often. But it was not always so. Freedom in using color as we see today was possible first in modern times, when chemists started to produce artists paints. Before the industrial advances in paint making the artists had a much more limited palette, which fact to some extend dictated the expressive qualities of art they created.
Take simple examples like Old Masters, or the colors of stained glass windows in Chartres (and other cathedrals). Old Masters had quite limited choice of pigments in comparison to modern times. Also very famous Chartres blue as a phenomenon is a mixture of technical skills and knowledge about chemistry which the makers of the stained glass windows possessed, but also accessibility of materials played strong part in it. We need to add in this mix also the symbolism of color during the Middle Ages, optical qualities of glass, philosophy relating to architecture which the windows were supposed to enhance, etc. Stained glass windows served as heavenly vision, were supposed to create awe, to be like precious stones, no less. And the medieval minds didn't create too much difference between the real precious stones and stained glass. So, freedom of expression was tempered by the requirements of functionality.
Blue was of course the color of the sky, spirituality, contemplation and symbolized divine wisdom. The luminosity of the stained glass itself represented spiritual illumination. Please click on the link to see the Notre Dame