Sexual selection may take place before or after mating and may involve a large number of different mechanisms, for example, overt male aggression, mate choice, sperm competition and cryptic female choice. In most species, males show similar reproductive tactics and, hence, achieve their reproductive success in the same or a similar way. Sometimes, however, males evolve alternative reproductive tactics. One such example is the polychromatic Australian painted dragon lizard, Ctenophorus pictus, in which red males beat yellow males in staged contests for females and show different emergence patterns post-hibernation in the wild with red males emerging to establish territories before yellow males do (at least in some years). Here we show that yellow males have significantly larger testes in relation to body size and condition than red males and copulate for a shorter period of time. Our mating experiments further showed that sperm storage played a significant role in male reproductive success (i.e. males sired offspring in later ovarian cycles than the one in which they actually mated). Furthermore, yellow males had a three times higher probability of paternity in some situations of sperm competition than red males, suggesting that male polymorphism may be associated with different reproductive tactics.