The observed color of a substance can be determined from the color of the light absorbed. What is “seen” is the complimentary colors.

When light passes through a material some wavelengths are absorbed. If absorption occurs in the visible region of the spectrum, the transmitted light is coloured with the complementary colour to the colour of the light absorbed. Absorption in the visible and UV regions of the spectrum is caused by changes in electronic energy (it is called electronic spectra).

 

Discuss the charge transfer as a source of colour