Wavelength and Colour in Coordination complexes
Low spin (formed from strong field ligands) complexes result in a larger difference in energy between the $t_{2}g$ and $e_{g}$ orbitals. High spin (caused by weak field ligands) complexes are, evidently, the opposite.
This means thats high spin complexes require lower energy photons than low spin. Since wavelength and frequency are inversely proportional, high spin complexes require lower frequency (longer wavelength) photons to promote transitions.