Color makes up so much of vision, yet it seems mnemonic. For example, this red colander from the dollar store and these red apples near it are about the same color, but the similarity is superficial. What makes the fruit skin red and the plastic red are not the same. While the redness of the apples tells me a smidge about ripeness, the redness of the colander tells me nothing of the sort; it's a decoration. The colander is red for a sensory pleasure of redness. We seem to use color to help us distinguish among items, but not, day to day, to tell us in absolute terms what they comprise.

When we go for a walk and look at things, their colors often tell us very little. If we were more scientific, the colors might help us identify materials on a molecular level. But the colors in themselves do not tell us much. Objects that reflect red do not seem to share anything else with each other, in general.

When we look out into the universe, the picture is a little different. Wavelengths of light are among our best resources for identifying what elements and compounds our telescopes detect. Yet when we look around us on Earth, colors help us sort objects and materials but tell us little to nothing about their character. White may evoke purity for some, oppression for others; even for the same people and same items, these reactions may be evoked at different times. When I see blue sky and blueberries, the similarity of hue tells me nothing, so far as I can see. Yet I know that clear daytime skies and the light dusty patches on those berries look similar, despite, I think, having nothing in common beyond a relatively small wavelength gap.