Structural Colours in Feathers

IN pigment colour we have absorption of light due to the molecular structure of the substance under observation. We speak of structural colours when the observed colour is due to, or is modified strongly by, the physical structure. Typical cases of structural colour are observed with prisms, diffraction gratings, thin films, and turbid media. In the case of feathers we find that the blacks, reds, oranges, yellows, and browns are pigment colours, but that the ordinary blues and greens are not blue and green by transmitted light, and that the so-called metallic or iridescent colours, such as those of the peacock, are structural colours.