ABSTRACT In this research it was evaluated the effect of background color on the development of the chromatophores in Macrobrachium tenellum prawns, six juvenile prawns were exposed to five background colors: black, white, pink, red, white and green; each one in triplicate, for 60 days. The development of the chromatophores was evaluated by means of the chromatophores index using a scale of 1 (the maximum concentrated pigment) to 5 (the maximum dispersed pigment). The coloration was analyzed in four anatomical regions of the organisms with the HSB model (hue-saturation-brilliance). The results show that the prawns modify their pigmentation according to the different background colors of experimental aquariums.