Sarah asked me the other day, "Why is snow white?" The child recently asked me, "Where do paisleys come from?" I was able to answer the latter question via Wikipedia, so I tried a Google search to answer the question about snow. Here's part of what I found:
Snow is a whole bunch of individual ice crystals arranged together. When a light photon enters a layer of snow, it goes through an ice crystal on the top, which changes its direction slightly and sends it on to a new ice crystal, which does the same thing. Basically, all the crystals bounce the light all around so that it comes right back out of the snow pile. It does the same thing to all the different light frequencies, so all colors of light are bounced back out. The "color" of all the frequencies in the visible spectrum combined in equal measure is white, so this is the color we see in snow, while it's not the color we see in the individual ice crystals that form snow.
I'm going to tell her that magic fairies paint the snow white.