Rare earth based materials have recently attracted considerable attention as potential eco-friendly colourants for low temperature as well as high temperature applications. In the present study, we have synthesized a series of Ca-doped PrPO4 compounds with the general formula, Pr 1-xCaxPO4 (x = 0-0-4 in steps of 0-1) and characterized the compounds by powder X-ray diffraction. All the compositions show a monoclinic monazite structure. The optical properties of the brilliantly coloured pigments [L (brightness), a* (+ red – green), b* (+ yellow – blue)] have been examined. These materials can find application as potential green colourants. © Indian Academy of Sciences.