When we look out on the world we see a rich tapestry of colors. Colors are not just adornment or luxurious sensory experiences, they also provide important information about the world around us. The region of the electromagnetic spectrum that contains light at frequencies and wavelengths that stimulate the eye is termed the visible region of the electromagnetic spectrum. Color is the association the eye makes with selected portions of that visible region.

This distinction is not trivial. Indeed, the colors we ordinarily assign to objects are not directly a part of the object. The oceans and sky are not blue--we perceive them as blue. The blue light that we see in the sky has been selectively filtered from sunlight by the interaction of the sunlight with gaseous and water molecules in the atmosphere that differentially (i.e., to a different degree) absorb, transmit, and reflect the wavelengths...