COLOR is a phenomenon of perception not an objective component or characteristic of a substance. Color is an aspect of vision; it is a psychophysical response consisting of the physical reaction of the eye and the automatic interpretive response of the brain to wavelength characteristics of light above a certain brightness level (at lower levels the eye senses brightness differences but is unable to make color discriminations). ( 1 ) That light is the source of color was first demonstrated in 1666 by Isaac Newton, who passed a beam of sunlight through a glass prism, producing the rainbow of hues of the visible spectrum. This phenomenon had often been observed before, but it had always been related to latent color that was said to exist in the glass of the prism. Newton, however, took this simple experiment a step further. He passed his miniature rainbow through a second prism that reconstituted the original white beam of light, His conclusion was revolutionary: color is in the light, not in the glass, and the light people see as white is a mixture of all the colors of the visible spectrum. ( 2 ) The reason rainbows appear colored is because the light is broken down into its constituent parts by passing through the water droplets in the air. (Sorry, no pot of gold. The perception of color in a rainbow is proportional to the viewer's perspective, you move, it moves.) The theory of color has gone through some changes over time, and it is now an accepted fact that color is truly in the eye of the beholder. "This is due to the fact that, as sensed by man, color is a sensation and not a substance." ( 3 ) Different people can also see color differently. We all agree the sky is blue, but a piece of reflective art may look slightly blue to one person while another sees it as slightly cyan. If you don't know the difference between the look of blue as opposed to cyan then communicating your preferences to a technician can be problematic. Subtle color variances are best seen under correct viewing conditions (not by a window, etc.) and can take some time to learn to even see them. Then when you can both see and discern these differences, then comes the task of communicating your choice for correction to a technician in the right terms (something I will cover soon). I'm always interested in discussion, scientific or otherwise. You can Email me at jscruggs@bway.net ( 1 ) ICP Encyclopedia of Photography Back ( 2 ) "COLOR" Time Life Library of Photography Back ( 3 ) History of Color Photography (1947) Joseph Friedman Back ( additive )( autochrome )( film )( grainmaker specifics )( screens )( subtractive )