Coloured Problem!! We know that transition metal ions have unpaired electrons in the outermost shell of the d and f orbitals. These unpaired electrons absorb a particular wavelength from visible light and are promoted to higher energy levels. Thus they reflect light of complement wavelength of the absorbed wavelength. If the incoming light is white(containing light of all wavelength) and the ion absorbs green light for instance then it would reflect a mixture of red and blue wavlength (i.e. magenta). Our eye recongnize the substance as magenta couloured. When the electrons come back to ground state, they would emit light of the wavelength previously absorbed(i.e green here). Here I am confused. What the compound would look like? Green or magenta? Here how I think about the problem. We can resonably assume that the lattice of the substance is composed of a large number of ions. At any instance of time some electrons will absorb light and some other will emit light. Then some portion of the substance would look green and other portion magenta. If both of this happen million of times in a tiny area we will not able to detect distinct colour, rather things will mix up and overally we should see white colour. I know there is some flaw in my analysis! What are the flaws? Another question: Is the exitation and de-exitation of electrons (quantum jump from one orbital to other) is the only reason that gives the subtances the colours they have? Does compound other than transition metal have colour? Your sensible answer will broad my understanding. Thanks in advance.