Why do things look darker when they are wet?

Question

Why do things look darker when they are wet?

Answer 1

Because when something is wet, light bounces around inside it more (as opposed to merely bouncing off the surface) before being reflected back to the eye. The more the light bounces, the more of it gets absorbed, the less reaches the eye, and the darker the object appears.

Answer 2

It's because light bounces around more in the material when it is wet, so more gets absorbed. (More may be transmitted, too - try holding a piece of paper with a wet spot up to the light! - but when the color is darker, it is because of absorption.)

The thing with color is: except when an object makes visible light on its own (e.g. when it is very hot), whatever color you see is the light reflected off the object. Nealy every time light strikes a surface, a fraction is absorbed by that surface - a small fraction, if it is white, but a fraction. If the light strikes a lot of surfaces, most of it will be absorbed. (This is why holes are dark - the light has to bounce around inside a lot before it has any chance of escaping, and most of it gets absorbed instead.)