An exciting EU project LODIS researched the genetics behind iridescence in bacterial colonies. The researchers explained the concept of this special type of colouration which is also at the base of the stunning beauty of many butterfly wings and mother of pearl.
Colours that look different when viewed from varying angles are termed iridescent. While pigment produce colours via a mechanism that is called absorption (they absorb part of the visible spectrum and what is not absorbed is eventually the colour of the object), structural colours are obtained by structuring material at the scale of the visible light wavelength. Such iridescent colouration can therefore change colour and brightness with the angle of view, a classic example is the mother-of-pearl lining an oyster shell.
Further details: Iridescent mutant bacteria provide a sparkling new palette!