linguistic:paraphrasing
Iridescence and structural coloration

As with many birds, vibrant iridescent plumage colors are not primarily pigments, but structural coloration. Optical interference Bragg reflections, based on regular, periodic nanostructures of the barbules (fiber-like components) of the feathers, produce the peacock's colors. 2D photonic-crystal structures within the layers of the barbules cause the coloration of their feathers. Slight changes to the spacing of the barbules result in different colors. Brown feathers are a mixture of red and blue: one color is created by the periodic structure and the other is created by a Fabry–Pérot interference peak from reflections from the outer and inner boundaries. Color derived from physical structure rather than pigment can vary with viewing angle, causing iridescence.