The shape of a snowflake is complex, but it can be described as a six-sided prism, or a hexagon with six equal sides. The flat surfaces of the ice crystals in snowflakes reflect light in all directions, which gives snow its white appearance.
In addition, the air in the atmosphere contains tiny particles of dust, smoke, and other impurities. When light from the sun hits these particles, it is scattered. This scattering is called "Mie scattering," and it is what gives snow its white color.
The amount of scattering that occurs depends on the wavelength of the light. Shorter wavelengths, such as those of blue and violet light, are scattered more than longer wavelengths, such as those of red and orange light. This is why snow often looks blue or purple in the shade, but it appears white in direct sunlight.
The shape and size of snowflakes also affect the way snow appears. Larger snowflakes tend to reflect light more efficiently, making them appear brighter. This is why fresh, fallen snow often appears brighter than old, packed snow.
Finally, the temperature and moisture content of the air can also affect the appearance of snow. Warm air holds more moisture than cold air, so snow that falls on warm days tends to be denser and wetter, which makes it appear darker. On the other hand, snow that falls on cold days tends to be drier and fluffier, which makes it appear lighter.
