Sir Isaac Newton discovered in the 1600s, that sunlight has no color and appears to be white. But this “white” light actually contains the seven colors of the rainbow: red, yellow, orange, blue, green, violet, and indigo. When light hits an object it may absorb, reflect, scatter, or transmit individual wavelengths, or shades of color back to our eyes.
Snow is made of tiny crystals. When light hits, it’s scattered by a zillion ice crystals. Sometimes on very sunny days you might catch little rainbows reflecting in the snow crystals. No one wavelength is absorbed or reflected, so snow to our eyes is white, the color of the sunlight.
Because water absorbs the red end of the visible spectrum, our eyes see the reflected blue color, the complementary color of red. An intense blue color is also reflected back from deep holes in fresh snow and glaciers.