Research has shown that men perceive women wearing red, relative to other colors, as more attractive and more sexually receptive; women’s perceptions of other women wearing red have scarcely been investigated. We hypothesized that women would also interpret female red as a sexual receptivity cue, and that this perception would be accompanied by rival derogation and intentions to mate-guard. Experiment 1 demonstrated that women perceive another woman in a red, relative to white, dress as sexually receptive. Experiment 2 demonstrated that women are more likely to derogate the sexual fidelity of a woman in red, relative to white. Experiment 3 revealed that women are more likely to intend to guard their romantic partner from a woman wearing a red, relative to a green, shirt. These results suggest that some color signals are interpreted similarly across sex, albeit with associated reactions that are sex-specific.