Pearlescent pigments are universally employed in all kinds of paints and coatings and allow a wide range of colours and effects to be achieved. For outdoor applications and especially for use in automotive coatings, these pigments have to meet very stringent requirements on weatherability. The majority of pearlescent pigments consists of a transparent substrate, such as mica, glass, silicon dioxide or aluminium oxide, which is coated with one metal oxide layer or a sequence of different metal oxide layers of different refractive index. Pigments structured in this way exhibit colour interference [1]. Due to its high refractive index of 2.55 ...