Animals often change their colour throughout ontogeny; however, the triggers for ontogenetic colour changes (OCC), and how this interrelates with the ability of individuals to perceive their environment remains largely untested. Here, we investigate OCC in the dusky dottyback, Pseudochromis fuscus. As adults, dottybacks are aggressive mimics that flexibly change colour to impersonate various fishes in their surrounding to increase access to their juveniles, upon which they prey; however, little is known about the early life stages of this fish.  Using a developmental time-series and combining it with wild caught specimens we describe multiple OCC events during dottyback development. Moreover, microspectrophotometric (MSP) and quantitative real time PCR (qRT-PCR) experiments show developmental changes of the dottyback visual system, including an adult specific expression of a previously undescribed visual gene (opsin). Modifications of the visual system precede OCC and based on theoretical fish visual models, this is likely to be because dottybacks need to be able to distinguish between the fish they are meant to impersonate, before colour changes can occur. Our results show how development and plasticity can interact to shape an individual’s life history, and dottybacks provide a good example of this adaptive ingenuity.