 The skin colour of amphibians is produced by three layers of pigment cells called chromatophores . These three cell layers consist of the melanophores ( occupying the deepest layer ) , the guanophores ( forming an intermediate layer and containing many granules , producing a blue @-@ green colour ) and the lipophores ( yellow , the most superficial layer ) . The colour change displayed by many species is initiated by hormones secreted by the pituitary gland . Unlike bony fish , there is no direct control of the pigment cells by the nervous system , and this results in the colour change taking place more slowly than happens in fish . A vividly coloured skin usually indicates that the species is toxic and is a warning sign to predators . 
