The highly-polymorphic, strongly-coloured 'ROY' system exhibits a yellow → orange → red piezochromic response under hydrostatic compression. The 'Y' (yellow) polymorph accommodates the effect of pressure via a wine-rack-type mechanism, made accessible by the conformational flexibility of the molecule, while retaining the crystal symmetry of the parent Y form. Decompression from 1.49 GPa demonstrates reversibility of this behaviour.