The contribution of sexual selection to speciation is a growing field. In particular, female mate choice has recently been examined as a mechanism for producing divergent mate preferences. However, less attention has been put towards understanding the sensory processes involved in perceiving sexually selected traits and how they may shape mate preferences. Sexual selection by female choice relies on males successfully signaling their fitness to females. If perception of the male’s signal varies among females, this could drive divergence in the male signal. Here, I test for differences in color vision between morphs of the color polymorphic poison frog, Oophaga pumilio. Females of this frog species generally prefer to court with males of their own color morph. I hypothesize that differences in the opsin proteins responsible for light absorption in the retina of the eye contribute to differences in color-associated mate preferences. To test this, I compare opsin expression levels and opsin sequences among color morphs. My results contribute to understanding how divergent mate preferences are formed, an important step on the path to speciation.