Question

Why is sonw is white but water has no colour

Answer 1

snow is white in colour because it absorbs all the colours and reflects white colour whereas water absorbs all colours and reflects blue colour of the sky.

Answer 2

The colour of an object is simply a combination of the frequencies of light it reflects. When light goes through a material, it bends depending on the density difference between the two mediums and other variables. With snow, there are so many little snow flakes that inevitably the light refracts back to the eye, which shows white. (A super thin layer of snow would seem transparent)

Water, without a ton of surface changes which allow refraction to bend the light, seems transparent/colourless. (Multiple droplets of water in close proximity would bend light enough. This is the principle behind a rainbow!)