Snow is white, because light rays do not penetrate the snow, and, since sunlight is pure white light, the snow, reflecting this sunlight appears white. Since snow is made up of billions of little snowflakes that all have reflective surfaces, the light rays bounce around in every direction but cannot penetrate the snow. The mixture of these light colors reflected back combine to make the color, white.
It is only when the light rays, red and yellow, can go further into the snow or ice, and are dispersed without being bounced back out, that the snow appears blue. The blue rays are the only ones left, because the reds and yellows tend to disperse more easily.
Snow banks and glaciers, as they grow in size and are more compacted, break up the little crystal snowflakes that produced them in the first place. This reduces the reflective capability of the snow, and allows the light rays to get deeper into the snow or ice. Since more of the light rays are absorbed rather than reflected, the longer blue light rays can penetrate the snow or ice and cause it to appear blue.
It was once believed that the appearance of the blue color in glaciers was dependent solely on the size of the glacier or the age. This is true, partly, but we now know that it has more to do with the inner consistency of the glacier, or snow bank, and, its ability to absorb the photon rays from the sun.
It is true, however, that the thicker the ice or snow, the more blue will appear. It takes a fairly thick piece of ice or pile of snow before all the red rays are absorbed, leaving only the blue.
The thickness of the glacier or the snow bank determines the compaction of the little air bubbles that reflect the light. As the ice or snow melts and refreezes, the air bubbles are squashed more and more. This allows the light rays to penetrate, instead of being reflected.
If you dig a hole in the ice, or in a snow bank, the colors you encounter actually depict the length of the photon rays. The color in the hole will vary the deeper you get, from yellow to yellow-green, to green, to green-blue, and finally to blue.
Through the years, mountain climbers and other arctic explorers have always known that camping or hiking on blue ice is safer than white because it is far more solid and compact.
http://www.gi.alaska.edu/ScienceForum/ASF7/773.html
