Where does the color go when the sun fades things?

Answer 1

In very low light, we use the rods cells in our eyes (as opposed to cone cells) to see (ie. night vision). Only cones are sensitive to colour. From http://en.wikipedia.org/wiki/Rod_cell: "Since rods require less light to function than cones, they are therefore the primary source of visual information at night (scotopic vision). . . . Because they have only one type of light sensitive pigment, rather than the three types that human cone cells have, rods have little, if any, role in color vision." See also link below. The color that we see is not from the color of the object itself, however, it is the colored light waves the bounce back from a light source that we perceive as a colored image. In other words, when there is not light source, there are no light waves bouncing of an objecting, reflecting the colors, and thus making it look black or colorless.

Answer 2

When the sun fades things, particularly fabrics or other colored materials, it breaks down the chemical bonds that provide the material with its color. This process is known as photodegradation, and it can cause the color to appear to fade over time, as the material is exposed to sunlight and its energy breaks down the colored molecules.