The Dark Factor mutation was first discovered in the 1920s in its double factor form, now called Olive (pictured third). As its name suggests, its body color becomes a darker olive shade. The single factor form was discovered shortly after, a slightly lighter green bird called Dark Green (pictured first). Combined with Blue, DF Dark Factors are known as Mauves (pictured fourth), while SF Dark Factors are known as Cobalts (pictured second).
Although Olives are quite similar to Grey Greens in color, they can be set apart by their normal-colored wings, tail, and cheek markings.
