.Usually green is selected if human performers will be in the shot. Historically blue was used if human performers were going to be in the shot, since it was most opposite in chroma phase to skin colour. The proliferation of blue jeans in the 1960s, and the fact that occasionally blue-eyed talent would have their eyes disappear gave way to using a bright green as the most common hue. Chromakey can, however, be used with any colour you wish.