Color and Properties of Oxygen in

Different States

Now the question is:

What is the color of oxygen? Well, gaseous oxygen is colorless. However, when in

liquid form, it comes in a shade of pale sky-blue.

Liquid oxygen in a beaker, showing its characteristic

pale-blue color. Credit to U.S. Air Force photo/Staff Sgt. Jim Araos, via Wikipedia.

The color of solid oxygen, on the other hand, ranges from light blue, pink-to-faint

blue, faint-blue, orange, dark-red-to-black, and metallic in six of its different possible

phases.

You basically can have solid dioxygen in 6 different phases. And each of them display

a particular color.

Why Is Liquid Oxygen Blue?

Similarly to what happens to water (which is also blue, by the way!), the energetic transitions of

the electrons in oxygen (which are also the cause of its para magnetism) absorb light on the red

spectrum. So red light is absorbed to some extent, giving the substance its complementary color:

blue.

If you want more info, this paper in the Journal of Chemical Education gets you covered.