system
Given the following post, respond as if you're commenting on Reddit:
human
When colors on fabric or paper fade from sunlight, where does the color go?

Does it just float away?
gpt
When a fabric has colour it is caused by a dye or pigmentation. 
Colour is caused by deflecting or absorbing certain wavelengths of light.
Dyes are chemical species which absorb light to provide a specific colour due to their particular structure. When exposed to chemical reactions like photodegredation (light breaking down the chemicals) or bleaching it will cause the chemical dyes to break apart and lose their shape, stopping them from absorbing that light.