Why does water make things appear different colors?

Question

Such as when your hair is wet, or when you spill water on your shirt, and the color is darker.

Answer 1

You have to remember about water's physical property. Water surface acts similarly as a surface of a mirror. A mirror tends to reflects light rays, so when you look at a mirror you can see your image reflection. ( which is as beautiful and colourful as your face is)

The same thing happens with water surface. It has got similar reflection properties. When you look at a river water surface, you can see your face.

What I said above is a proof that water is a good reflection surface and when light ray falls on its surface, it seems to be brighter...as  water surface does not absorbs the light falling on it, instead acts like a mirror reflecting back the ray and looks brighter and colourful.

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Now. the answer to question... ( Taking granted for the above assumption)

if a dress or shirt ( Any colourful cloth) is dry , it is less reflective means absorbs the light rays instead of reflecting...so. seems to be less bright or colouful.

But if the cloth is wet, there is water in the fibres and  these water molecules are so reflective like a mirror surface...so, colours of the cloth fibre apparantly seem to be more colourful and vivid.

That is your appreciation as you have mentioned in your question.

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Your wet hair behaves in the similar way, when it is dry, it does not look shiny and silky. You feel  your hair is oily or not shining.

But after shampooing your wet hair becomes colourful, shiny and silky.

The effect of your hair colour is more visible in wet state, and  if you go out under the sun light or stay in a bright lighty room, the colour effect is much more impressive and eye catching.

The wet hair, with water in it, reflects the light rays and gives an brightful appearance AS IF they were so colourful.