Prior work has shown that the orange-red coloration of male zebra finch beaks, which is a carotenoid-based signal used in mate choice, is perceived by females categorically (i.e., either as “orange” or “red”), not in a continuous fashion. The Bengalese finch, an estrildid related to the zebra finch, is black, brown and white, and lacks carotenoid coloration. To explore the relationship between categorical color perception and signal use, we tested Bengalese finches using the same orange-red continuum as was tested in zebra finches. Bengalese finches did not exhibit categorical perception; instead, differences in brightness appeared to better predict discrimination ability. We further tested both species with colors that differed systematically in both hue (i.e., chromatic distance) and brightness (i.e., Michaelson contrast). Chromatic distance and brightness contrast correlated with color discrimination ability in Bengalese finches, while in zebra finches this correlation held only for between-category discrimination, not for within-category discrimination. These results suggest that categorical perception is not a general feature of avian visual systems and supports the possibility that this perceptual mechanism is adapted for signal function.