Banner photo: There are no natural blue pigments in biological tissues, yet the South American morpho butterfly (Morpho peleides) has resorted to optical tricks to produce lustrous  blue tones. The butterfly uses thinly spaced chitin plates and ridged structures that reflect blue wavelengths to produce their wing colors. While layers of wing scales are transparent, the repeated plates and ridges diffract and reflect light to give the scales their iridescent appearance.
Photo (C) lee james flickr.com/photos/129513836@N08/