The marketing value of ornamental crops is attributed by several characteristics among which colour is considered the most critical character. Development of flower colour is influenced by many internal and external factors which may also be specific according to the species. It is crucial to understand the underlying mechanisms of colour development and functions of the pigments involved. There are several works that outlines the biosynthetic pathway of these pigments and their role in establishing flower colours. Certain attempts have also been made to modify flower colours using recent advances and genetic engineering has proved successful in acquiring novel colour in some ornamental species. This chapter covers the pigments involved in colour development of flowers, their structures, biosynthesis as well as approaches to regulate colour in ornamental crops.