Animals as diverse as cephalopods, insects, fish, and mammals signal their social dominance to conspecifics to avoid costly fights. Even though between-species fights may be equally costly, the extent to which dominance signals are used between species is unknown. Here, we test the hypothesis that differences in color are associated with dominance between closely related species that aggressively interact over resources, examining between-species variation in colors that are used in within-species badges of status (black, white, and carotenoid coloration) in a comparative analysis of diverse species of birds. We found that dominant species have more black, on average, than subordinate species, particularly in regions important for aggressive signaling (face, throat, and bill). In addition, dominant species were more likely to have more black in comparisons in which the dominant species was not larger than the subordinate species, suggesting a greater importance of black as a signal when other signals of dominance (size) are missing. Carotenoid colors (i.e., red, pink, yellow, and orange) were not generally associated with dominance across all species but may signal dominance in some taxonomic groups. White appeared to have opposing functions in dominance signaling: white was associated with dominance in species in which black was also associated with dominance, but was associated with subordinance in species in which carotenoid-based dominance signals may be used. Overall, these results provide new evidence that colors may function broadly as signals of dominance among competing species. Such signals could help to mediate aggressive interactions among species, thereby reducing some costs of co-occurrence and facilitating coexistence in nature.