Behavioral response, Acetylecholinesterase activity, total protein level and protein fractions of the Nile tilapia, Oreochromis niloticus were investigated after 37 days exposure period to different environmental colors (Yellow, blue, green, red and darkness). Groups of 10 individuals each with initial body weight of 10.01±0.15 g were reared in 60x30x50 cm) aquarium. Two replicat...