Avoiding detection by appearing cryptic is a common trait that can be found in a wide variety of taxa. However, a general camouflage functions poorly when organisms experience spatial and/or temporal environmental heterogeneity. The ability to change colour (phenotypic plasticity) enables individuals to adjust their camouflage to that of their current environmental conditions. Yet, there’s a large gap in knowledge regarding the drivers and mechanisms associated to the evolution and maintenance of the ability to colour change. In this thesis, I examined several different traits related to stickleback’s (Gasterosteus aculeatus) capacity to colour change. The sticklebacks (sampled from the Baltic Sea) were exposed to two different backgrounds, one bright (white) and one dark (black). The colour change that occurred in both backgrounds where recorded with a high-quality video camera (4k), and analysed using an image software tool. The results showed that; 1) sticklebacks adjust their dorsal colour to match backgrounds (background matching); 2) that they were consistent in their intra-individual colour change;  3) that an increased background matching might be induced by a perceived predation risk; and 4) that individual sticklebacks differ in their capacity to colour change (phenotypic variation). The ability of the sticklebacks to consistently adjust their dorsal coloration to each background, and the notable differences in ability to colour change indicate that the capacity to colour change in fact is a trait in wich selection can act upon. Whether the trait is heritable, and in what degree the capacity to colour change is related to a genetic component remains to be determined. The predation risk experiment also suggests that the ability to colour change in fact is a mechanism of an environmentally induced camouflage (via background matching). These findings provide a first insight into ecological and evolutionary questions related to the ability to colour change (and phenotypic plasticity), paving the way for future studies related to the adaptive value of colour change, and how different environmental conditions influence the evolution of colour change.