where does the white go when the snow melts?

Alnitaka answered it correctly. The water molecules refract the light differently compared to the ice crystals where the molecules are compressed tightly. The light passing thru' ice crystals gets refracted (means reflection) to all angles hence all seven colors of different wavelengths gets merged to become white to our eyes.

Why the rain clouds are darker? Because the light gets absorbed by the water molecules in the air and hence we see black clouds.

Snow crystals and liquid water reflect light differently. When snow melts, the structure that reflects all the visible wavelengths into your eye (causing the white color) changes so that light waves go through the liquid before reflecting instead, causing the clearness of liquid water.

The white on the ground melts, temporarily remaining colorless liquid while it waits to turn into its heat treated state to rise into the atmosphere where it cools and returns as white clouds.

Santa Claus and his elves pick it up every night when you're sleeping and keep it at the North Pole until next year.

snow is the white stuff so you answered your own question