COLOUR OF COMPLEXS
See here actually on the approach of a ligand the initially degenerate d orbitals now split ut into two energy levels Eg and T2g levels which are of two forms octahedral and tetrahedral splitting
Eg consists d(x^2-y^2) and d(z^2)
T2g consits d(xy),d(yz),d(xz)
so when an electron at a lower energy level absorbs light from outside and jumps from one lower energy level toa higher one you are able to see the light that is reflected ie if Cu complex is blue in colour that means the electrons have absorbed red colour to jump up!!!
now your doubts clarified!!!?????