system
Given the following post, respond as if you're commenting on Reddit:
human
What causes pictures to appear discoloured after being in direct sunlight for years at a time?

Just clearing out some old Xbox games and the logo on the side of them have turned blue after being in sunlight untouched for several years?
gpt
The effect is called photodegradation.

The part of a material responsible for it's color is called a chromophore. A chromophore is just a group of atoms in a molecule which are responsible for the molecule's 'color' - they have a specific absorption / reflection spectrum.

Sunlight can cause reactions in the molecule which change the structure of the chromophore so that it no longer has that specific absorption spectrum. Usually what happens is that the molecule no longer absorbs visible light, and now appears white. The more molecules are affected like this, the more bleached or white the paint will appear.