but is not the color a function of the wavelength?!?
As an observer of color, I see light **only** in the aqueous humor of my
eye, therefore whatever medium it was in prior to entering my eye is
immaterial. Likewise if I record it on film, the color is found in the
gelatin base of my film. I see no way of measuring color. I can measure
frequency or I can measure wavelength, but color is a slippery concept,
tied so closely with human perception.