The colours of most species are pigmentary (via papiliochrome); but two species, "Troides magellanus" and the much rarer "T. prattorum", are noted for their use of limited-view iridescence: the yellow of the dorsal hindwings is modified by bright blue-green iridescence which is only seen when the butterfly is viewed at a narrow, oblique angle. This "grazing iridescence" is brought about through diffraction of light (after back-reflection) by the wings' extremely steeply-set, multilayered rib-like scales (rather than the ridge-lamellae of most other iridescent butterflies, such as "Morpho" species). Such limited-view iridescence was previously only known from one other species, the riodinid "Ancyluris meliboeus". In "A. meliboeus", however, the iridescence is produced by ridge-lamellar scales and features a wider range of colours.