Polar bear fur is made of clear hollow tubes. Those countless tubes cover a skin that is black. Yet, polar bear fur looks white.

Have you ever seen hail that is colorless? Why is that, when hail is primarily frozen molecules of water pressed together?

Cumulonimbus clouds are those towering, thunderous, and ominous looking monsters. Capped with a mushroom or an anvil-shaped top that is pure white.

It is a given that boats, ships, jet-skis have a white tail. This is the foamy aerated water that is churned up as the boat makes it way forward.

Egg white proteins are translucent; however, when whipped they become pure white. 

The same concepts that creates foamy liquids creates sea foam. Except the foaming bubbles that are part of sea foam last much longer than those in a glass of soda. 

The gas that produces the "head" in a pint of beer is carbon dioxide, though nitrogen is sometimes added to produce a longer lasting, less acidic taste. 

The tops of clouds are the whitest. Take a look, sometime, at how pure white they can be.

Blinding white snow. As white as snow. A blanket of fresh white snow. Those images are clear in our mind's eye. And the reason snow is white is the same as why clouds are white or polar bear fur is white.

Even soap colored green will form white bubbles of soapy foam. One could have black soap and still the foam will be a pure white.

Liquid water is white at the interfaces of water and air when there is turbulence.

Wave crests, breaking waves, waterfalls, the wake of ships and boats, river whitewater, water splashes, and water jets are all examples of turbulent water/air interfaces. 

It is not only air that creates a gas/liquid interface.  Shaking a can of soda will create a mass of white CO2 bubbles.