What is the color of water?

A raindrop looks completely transparent. However, when we look at a thick layer of ice, we notice that it is in blue tones. As the depth of the water body increases, the blue color becomes evident. When water molecules interact with light, it absorbs rays of red wavelength (~ 700 nm) in the visible region of the light spectrum. That is why the color of the water is in blue tones.

However, the mechanism that makes the water look colorful is a bit different than other substances that look colorful. The reason we see a substance in color is related to the wavelength of the rays it emits, absorbs or reflects. When a substance absorbs light of a certain wavelength, its electrons are stimulated and passes to higher energy levels, i.e. absorbed light causes electron transition. The rays that cause electron transition in the water molecule are in the ultraviolet wavelength.

When the water molecules absorb the rays of the red wavelength, the vibration energy levels of the water molecules change. This change is the reason why the water is seen in blue tones. In many other substances, rays of wavelengths longer than the wavelength of visible light cause a change in vibration energy levels.