Colour vision is the ability of an organism to distinguish objects based on the wavelengths or frequencies of the light they reflect, emit or transmit.
The study published in the journal Optica, states that our colour vision gives our eyes the ability to make a distinction between things that differ in thickness by just a few nanometers. That's about the thickness of a cell membrane or even the size of a virus.
The researchers at the University of Eastern Finland conducted various experiments and found that the human eye is able to identify changes in colour that correspond to film thickness differences.
Perception of colour begins with specialized retinal cells containing pigments with different spectral sensitivities, known as cone cells. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic colour vision. This is why the human eye can distinguish about 10 million different colours.