Snowflakes are white because they reflect most of the light that hits them. Since visible light is white and snowflakes reflect that light, snow generally appears white in color while falling through the air or blanketing the ground. Exceptions exist, however, and deep snow sometimes looks blue on the ground.
Deep snow sometimes absorbs red light from other sources bouncing off the ice crystals. In this case, the snow reflects a bluish tint. Snow that appears blue often lies underneath snow that appears white due to the distance the light travels. Red snow also exists due to environmental factors such as algae or the presence of salt water, particularly during the summer months.