This mutation was first discovered in 1934 by Australian breeder S. Harrison, buying a Grey (+Blue) individual from an unknown breeder. It potentially popped up twice more in Australia in the following years, adding further genetic diversity to the gene pool. Birds with this mutation have an army green body color similar to Olive, as well as black flight feathers, a black tail, and pale purple cheek markings. These features separate them from Dark Factors, which have normal-colored flights, tail, and markings. The SF and DF forms of Grey Green vary only slightly, with SFs having normal-colored (white) feather shafts and afterfeathers, and DFs having grey feather shafts and afterfeathers.
