Why color of alkali metal peroxides, superoxides and ozonides deepens down the group?
Most likely, we are seeing the same band structure effects.

There is an additional trend, whereby the compounds become darker and more reddish as one adds more oxygen.  In oxygen-chain species such as $\ce {O2^{2-}} $, antibonding molecular orbital are occupied.  So The valence band containg these electrons is raised.  That lowers the band gap enabling absorption of more visible light.

Incidentally, the visual effects described here are limited to alkali metal (when oxygen is the electronegative element).  When we move to the corresponding alkaline earth oxide the monoxides are white and the peroxides ($\ce {Mg}$ and heavier) are white too.  Less strongly ionic bonding and a lower cation/anions ratio lead to less negative charge on the oxygen species, thus lower valence band energies and gaps  remaining large enough to remain uv-absorptive only.