Snow is actually frozen water, and as we know ice has no colour, why then is snow white?
The reason is that each snowflake is made up of a large number of ice crystals. These crystals have many surfaces.It is the reflection of light from all these surfaces that makes snow look white.
Snow forms when water vapour in the atmosphere freezes. As the vapour freezes, clear transperent crystals are formed. The current that are in the air makes these crystals go up and down in the atmosphere.