Flat Periwinkle variation

Flat Periwinkle variation

Observation - Flat Periwinkle variation - UK and Ireland. Description: Allsorts; live and bright ones are hard to find; empty shells easy. The pair-pictures are live from the very same pool. Might this be camouflage adaptation or response to coloured food?

Allsorts; live and bright ones are hard to find; empty shells easy.
The pair-pictures are live from the very same pool. Might this be camouflage adaptation or response to coloured food?