A snowbank is white. An ice cube from your freezer is clear enough to read through. The deep ice inside a glacier crevasse glows a saturated blue that no winter sky can match. All three objects are frozen water, and nothing else — the differences come from structure and distance, not chemistry. Snow and ice are a clean demonstration that the color of a substance can live in its shape.
The U.S. Geological Survey states the underlying rule for the blue end directly: glacier ice is blue because ice absorbs the red, long-wavelength part of white light and transmits and scatters the blue, and the longer the light's path through ice, the bluer it appears. Everything in this article is just that one sentence meeting different geometries.
White is a structure
A snowflake is transparent, the way an ice cube is. A snowbank is white because it is not one crystal but a heap of them, stacked with air in every gap. Every ice-to-air boundary bends and bounces passing light — the same abrupt change of medium that makes a pond surface reflect the sky. In a snowbank, light strikes these boundaries millions of times, in all directions, at all wavelengths, and what finally escapes back out is a thorough mixture of everything that came in. That mixture is what we call white. It is the same logic that keeps a fair-weather cloud blinding white and a rain puddle transparent: droplets or crystals in aggregate scatter all colors together, while a single smooth sample of water lets light pass in order.
This is also why snow's whiteness is a property that can be destroyed without melting anything. Crush it, refreeze it, or let it settle and round into coarse grains, and the scattering network coarsens — old snow keeps its white but loses its brilliance as the crystal structure ages. The water never changed color; the light-handling architecture did.
The ice cube's short path
An ice-cube tray makes the counter-case. A household cube usually contains a scatter of tiny bubbles and still looks nearly clear, and a deliberately bubble-free cube — frozen slowly, or boiled first — can look like glass. The cube's millimeters and centimeters are simply too little runway. Ice does absorb a little red light, but in a short path the amount is negligible, and since little red is removed, no visible blue surplus builds up. What you see is the light that entered, essentially unedited, plus whatever the freezer's bubbles happen to bounce around.
That is the whole trick of the color spectrum of ice: absorption by path length. A centimeter of ice: nothing to see. A meter: a faint cool tint. Ten meters or more of it: unmistakable blue.
Screen swatches approximate appearances; the mechanism is the path length, not the exact hex value.
The blue that needs meters
Glaciers supply the long path. Snow falls, accumulates, and gets compressed under its own weight until the air spaces close and the mass becomes dense, transparent ice. The National Park Service describes the blue of glacier ice as the color of pure, compacted ice from which the air has been squeezed out. Deep inside — or along a freshly split crevasse wall — light travels through many meters of this material. The ice quietly absorbs its preferred wavelengths along the way; what survives and returns to your eye is the blue remainder. Deep glacier ice is thus one of the few everyday cases where color is earned by thickness: the interior blue is literally the sum of everything the ice removed on the way through.
Notice how the two mechanisms trade off. Bubbles — air boundaries — make ice white, and their absence lets ice be blue. The same glacier can show both in one frame: a milky, fractured white surface above, and glassy blue walls where the ice is solid and the view is deep. Frozen lakes do the same trick in winter: a snow-covered sheet reads white, while a cleared, bubble-free patch over deep water reads dark and faintly blue.
When the rules bend
Between the extremes, hybrids appear everywhere. Partially melted and refrozen snow can turn gray and dense, white ice forms on lakes when freezing is fast and bubbles stay trapped, and wind-packed snow develops a glassy crust that catches blue shadows. None of these are impurities in the ordinary sense — they are reorganizations of the ice-air geometry, each rewriting how far light travels inside solid ice versus bouncing off boundaries.
The payoff is a compact rule you can carry outside. White means scattered: light met a maze of boundaries and came back promptly. Clear means too little material to matter. Blue means traveled: somewhere, that light took a long route through solid, bubble-free ice, and the red it lost along the way is the reason the remainder looks the way it does. On the next clear day after snowfall, the drift, the icicle, and the frozen lake are all demonstrating it for free — and if you want to feel how narrow the boundary between a muted blue and a flat gray can be, Blue or Gray? lets you probe exactly that edge on your own screen, no glacier required.