iridescent

Iridescent describes a surface or object that appears to shimmer with different colors as the angle of view or illumination changes. The effect is not due to a single pigment but to the interaction of light with microstructures that cause interference, diffraction, or scattering. The term derives from the Latin iris, meaning rainbow, and ultimately from the Greek goddess Iris.

Most iridescent colors arise from structural coloration: thin-film interference in multilayer films, papillae or ridges on surfaces, or layered microscopic platelets. As light reflects from different interfaces, certain wavelengths are enhanced or canceled depending on the viewing angle, producing vivid shifts in hue.

Natural examples include butterfly wings (notably Morpho species), peacock feathers, opals, and mother-of-pearl in mollusk shells. These structures are often more iridescent than pigmented colors, because they produce hue by physical structure, not by chemical pigments.

Applications include ornamental coatings and paints that rely on interference pigments, cosmetics, and fashion. Iridescence is also used in anti-counterfeiting features, art, and various biomimetic materials inspired by natural structures.

The phenomenon depends on the viewing angle and light source; colors can shift or vanish as the observer or illumination changes. Iridescence is related to but distinct from pearlescence, which tends to produce more static, pearly colors.