The white of snow is due to multiple scattering off ice crystals. Dispersion Many materials refract different wavelengths differently, causing light to spread out into the colors of the spectrum. This mechanism is called dispersion. Rainbows are due to dispersion by water droplets, coupled with reflection off the back of the droplet. The overall red tone is due to scattering of red sunset light by raindrops.
Ice crystals can cause dispersion.
Some haloes around the Sun and Moon are due to ice crystals suspended in the atmosphere. This ground-level halo in Minnesota is due to windblown snow. Haloes close to the Moon are due to dispersion by water droplets rather than ice crystals. When light beams are split and recombined, they can undergo interference. Thin film interference occurs when light reflected from the two surfaces of a thin film interferes.