Male agama lizards display conspicuous, bright colours (such as a red head and blue body) during the breeding season to attract females and signal their reproductive condition. This is a specific example of mating coloration, a form of adaptive coloration used in social signaling.

B. variegated grasshopper uses bright colours primarily for warning coloration (aposmatism) to alert predators that it is unpalatable or poisonous, not for mating.

C. chameleon changes colour for various reasons, including camouflage, thermoregulation, and communication (e.g., expressing mood like fear or aggression), but these changes are related to many social contexts, not solely a specific "mating coloration" as a primary function in the same way the male agama lizard's seasonal change is.

D. leopard exhibits disruptive coloration (camouflage) with its spots, which helps it blend in with its surroundings to stalk and ambush prey unnoticed, rather than attracting a mate with bright colours.

The correct answer is option A