One of the questions I get asked most while zodiac cruising through glacier ice is why the ice is blue. Somehow this is strange even though nobody ever asks why the water in the ocean is blue… The explanation is the same. Light consists of different wavelengths (colours). Of these wavelengths blue travels the furthest through water (in liquid or frozen form). So if the water or ice is clear the light that will get the furthest is blue, colouring this water or ice blue. However, often there are other things in the ice or water.
This raises the question why most of the icebergs are white. Because glacier ice is formed by snow falling often there is a lot of air inside. This air reflects the incoming light quickly, before the other wavelengths have disappeared resulting in white light coming back out. When ice gets pressurised more, the air bubbles get more compressed (and smaller) which result in clearer and thus bluer ice.
Anyhow, however it’s formed, it’s a beautiful sight.