Female-specific reproductive coloration is widespread among lizards, prompting several hypotheses to explain the possible function(s) of such coloration in females. I tested four of these hypotheses using observational and experimental field studies of free-ranging collared lizard females, Crotaphytus collaris, which develop orange markings on the lateral torso in association with the reproductive cycle. Orange markings did not appear to function for advertisement to female competitors because females rarely displayed their coloration during interactions with consexual competitors, and markings developed well before the occurrence of peak aggression among females. By contrast, females frequently displayed their lateral torso when courted by males. The number of displays given to courting males did not differ in females that had and those that had not yet developed orange markings, suggesting that female coloration does not function for sexual recognition in collared lizards. Females developed orange pigmentation while they matured their first clutches, and markings were maintained between and throughout the production and oviposition of the second and third clutches. Male courtship encounters with females having naturally developed markings were longer and involved more male displays than those with females that had not yet developed their coloration, suggesting that development of coloration by females functions to stimulate male courtship when females are receptive. To test this hypothesis, I established nine female pairs of size- and age-matched females that had early vitellogenic eggs, but had not yet developed reproductive pigmentation. Female pairs were each residents on the territories of nine different males. One female in each pair was painted with orange spots and bars to mimic the natural orange coloration and the other with light brown to match the natural background coloration of female C. collaris and mask naturally developed pigments. Males began courting orange-painted females within 2 h, and, on average, orange females were courted over five times more frequently than brown females. The difference in courtship frequency did not appear to result from males avoiding brown females because the average distance between males and females in the two treatment groups was similar. These results support the hypothesis that reproductive coloration in C. collaris females stimulates courtship rather than signaling rejection of courtship to males.