The Ornamental fish trade in India and its export to other countries has shown an increasing trend with more and more people wanting to own an aquarium as a hobby and also for decorating their houses, hotels, and offices. Among these fish, Guppies are very popular ornamental fish. The guppy is commonly called the rainbow fish because of the numerous color patterns. Guppies show sexual dimorphism. For example, males are smaller in size than females and have a bright colored pattern. The guppy is one of the premier model organisms for the study of phenotypic variation. This variation is a consequence of different evolutionary and environmental contexts, including predators, carotenoid availability and female preferences. Variation in female preference for males is due to the variation in color development especially orange color. Color variation is influenced by many intrinsic and extrinsic factors. The intrinsic factors include the opsin genes expression responsible for color development in guppies.