Blue Diamond Prelude C&amp;GBlue Diamond Prelude C&amp;G Blue Diamond Prelude C&G The Blue Diamond Prelude (Colts and Geldings) is a Melbourne Racing Club Group 3 Thoroughbred horse race raced under set weight conditions, for two-year-old colts and geldings, over a distance of 1100 metres at Caulfield Racecourse in Melbourne, Australia in February. Total prizemoney is A$200,000. History. The race is a major preparatory race for the rich Blue Diamond Stakes held two weeks later. Colts that have captured the Blue Diamond Prelude – Blue Diamond Stakes double: Rancher (1982), Bel Esprit (2002), Sepoy (2011), Written By (2018) Blue Diamond Prelude C&G The Blue Diamond Prelude