Question

why the reflection of clouds not seen in water but reflection of sky's blue colour is seen

Answer 1

The sky appears blue, when viewed from Earth, because of the scattering of the light. Scattering is the phenomenon by which a beam of light is redirected in many different directions when it interacts with a particle present in atmosphere. When sunlight strikes molecules in our atmosphere, the light is scattered in many directions. The blue light is scattered more than the red light causing the sky to be blue.