In the guppies, Poecilia reticulata, males show various body colors and females prefer some components of these male colors. These color patterns are highly polymorphic and female preference also varies within and among populations. Females perceive male color patterns with their color vision, so these variations in female preference can be explained by the variations in color vision and its related genes. It was reported that guppy LWS opsin genes have high sequence variability. However, it is not clear whether the polymorphisms of the opsin genes are related to the variation of color sensitivity and female preferences. Thus, we first tried to detect the effect of LWS opsin genotypes on color sensitivity and female preference. We measured the light sensitivity of guppies using optomotor response. We determined LWS opsin genotypes of guppies and observed their response at four wavelengths. In consequence, at 532 nm, the light sensitivity differed depend on LWS opsin genotypes. This showed that difference in LWS opsin genotypes can have an effect on light sensitivity of a specific wavelength. We also performed mate choice experiments and examined the effect of LWS genotypes on female preference to male carotenoid spot.