Colour polymorphism in Podarcis muralis is discrete rather than continuous: males fall into white, yellow and orange classes, with intermediates in some populations. Genetic work has linked the morphs to variation at genes in the pteridine and carotenoid pigment pathways, which is why the colour is stable across an adult's life rather than shifting with condition.
Studies across European populations have reported morph differences in body size, bite force, stamina, immune response and aggression, with orange males often larger and more aggressive and white males more numerous. The associations are real but not consistent everywhere, and the temptation to map the system onto the neat rock-paper-scissors dynamic documented in the side-blotched lizard should be resisted; the evidence for cycling frequencies in wall lizards is much weaker.
The species is also a notable coloniser. Introduced populations in southern England, Ohio and elsewhere descend from small deliberate or accidental releases, and some have spread substantially. Where introduced wall lizards meet native lizards, competition effects have been reported but are not uniformly demonstrated.