Color vision under variable light environments is important for mate choice, food acquisition, and for reducing predation risks. Color vision is enabled by different spectral types of cone visual pigments which comprise opsins and chromophores. Spectral sensitivities in individuals vary with the expression levels of opsin genes, which may be altered according to light environments. Here we tested whether light environment during growth induced plastic changes in opsin gene expression and behavioral spectral sensitivity in guppies. Individuals growing under orange light exhibited higher expression of a long wavelength-sensitive (LWS) opsin gene (LWS-3) and higher sensitivity to 600-nm light than those growing under green light in adult stage. Our results indicate light environment during the growth stage alters the expression levels of LWS opsin gene and thus color vision. Plastic changes in color vision might lead to adaptation to variable light environments without much genetic variation, and provide a significant insight into studies of female preferences and the evolution of highly polymorphic male sexual colors in guppies.