Transition metal complexes have colour because the ligands bonding to the central metal atom or ion cause the d-orbitals to have different energies, that is, they are no longe … r degenerate.In octahedral complexes, the dx2-y2 and the dz2 orbitals are higher in energy than the dxy, dxz and the dyz orbitals.ransition metal complexes have colour because the ligands bonding to the central metal atom or ion cause the d-orbitals to have different energies, that is, they are no longe … r degenerate.