In Enallagma damselflies, female-specific color polymorphism is proposed to have evolved under sexual antagonistic selection to confuse the males, hence, reduce harassment. However, sexual antagonistic selection rarely ceases. When the female strategy incurs costs for the males, the males are expected to evolve counter-adaptation to reduce the costs. Indeed, males have been found to counter-adapt female color mimicry by using an additional cue of abdominal pattern to distinguish sex. Yet the crucial assumption that female color mimicry incurs a cost for the males remains untested. This study aims to measure the opportunity cost (i.e. loss of mating opportunities) of color mimicry of blue females, and its fitness consequences for male E. hageni.