The Blue Monkey or Diademed Monkey is a species of Old World Monkey native to Central and East Africa, ranging from the upper Congo River basin east to the Great Rift Valley and south to northern Angola and Zambia. It sometimes includes the Sykes', Silver, and Golden Monkey as subspecies. Despite its name, the Blue Monkey is not noticeably blue: it has little hair on its face, and this does sometimes give a blue appearance, but it never has the vivid blue appearance of a mandrill, for example. It is mainly olive or grey apart from the face.