Tantalum zirconium oxynitride phases Ta(3-x)Zr(x)N(5-x)O(x) (0 less than or equal to x less than or equal to 0.66) having the Ta3N5 structure and Ta(1-x)Zr(x)N(1-x)O(1+x) (0 less than or equal to x less than or equal to 0.28) with the TaON structure have been prepared by solid state-gas syntheses, Oxide precursors have been prepared by a novel sol-gel process variant, using a mixture of acetic acid and acetic anhydride as solvent. The optical properties of the brilliantly coloured pigment quality Ta(3-x)Zr(x)N(5-x)O(x) (0 less than or equal to x less than or equal to 0.66) semiconducting oxynitrides have been examined by UV-VIS remission spectroscopy. Their applicability for an industrial scale production and a widespread use as brilliant, lightfast and inert inorganic colouring agents has been investigated. These pigments may be useful for colouring paints, plastics and medium temperature ceramic applications, replacing comtemporary toxic metal containing pigments.