Guppies are important model system for the study of sexual selection for colouration which is an especially important component of female mate choice. Guppies own phenotypic variation to diverge natural and sexual selection by evolutionary (internal factors) and environmental factors (external). Internal factors include expression of different opsins with sequential variation along with copy number and influenced by many external factors like water quality, role of light, effect of protein, fat and carotenoid, mate choice and presence of predation. Studying all these factors will enable to predict the colour development with sequence variations in guppies.