Colour of metal complexes with the same type and number of ligands
When electrons come back down they emit the same wavelength of light and that's the colour we see.


I think this is a major misconception held by students. The color of these transition metal complexes is due to the absorption of light in the visible region. Very crudely, imagine you have six colors in the rainbow, if you remove a certain color portion from that rainbow, the transmitted light is no longer white to our eyes. For example, copper (II) absorbs red, that is why it appears blue to us. Yes, the electron has to relax back to its ground state, it does so non-radiatively. 

The spacing (∆o) in the energy level determines the wavelength which will be absorbed.