Why does a fabric become darker when is wet?

Question

When a cloth is wet, it appears to be darker than it actually is. why does its colour change to a darker shade?

Answer 1

Any dry cloth absorbs some frequencies of light. Any wet cloth absorbs some frequencies of light, as well as the frequencies of light absorbed by the water in it. Thus less light is getting reflected towards an observer overall - it's darker.

There is the possibility that on "shinier" stuff, where water isn't absorbed but is on the surface, that more light gets reflected off the surface of the water than goes into the water and gets absorbed by the cloth. So it isn't universally true that something with water on it will look darker. But yeah, when it is absorbed into the cloth, it seems to be the case that more light frequencies will be absorbed without the reflecting effect being a big deal.