OliveOlive, a recessive mutation, has only recently been developed and is still relatively rare. Olive birds have light grey feathers with a heavy yellow wash, making the feathers appear almost greenish. There seems to be some variation in the lightness of the grey among different birds — some are much paler than others. Olive birds also have a slightly scalloped pattern on their wing feathers; the edges of these feathers are darker, fading into slightly paler centers.