All surfaces absorb and reflect different wavelengths - it is reflected wavelengths that determine what colour we see. When separated, any single wavelength will produce a specific colour impression to the human eye. Each colour has its own properties that form its wavelength, from violet with the shortest wavelength through the colour spectrum to the reds which have the longest.
The more pigmented your paint is, the more wavelengths are created and therefore the greater the perception of depth. Aalto colours are all individually built to allow for the full interplay of light and pigment.