Grey aliens, also referred to as Zeta Reticulans, Roswell Greys or Grays, are purported extraterrestrial beings. They are frequent subjects of close encounters and alien abduction claims. The details of such claims vary widely, however Greys are typically described as being human-like with small bodies, smooth, grey-colored skin; enlarged, hairless heads; and large, black eyes. The Barney and Betty Hill abduction claim, which purportedly took place in New Hampshire in 1961, popularized Grey aliens. Precursor figures have been described in science fiction and similar descriptions appeared in early accounts of the 1948 Aztec UFO hoax and later accounts of the 1947 Roswell UFO incident.
Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate the color used as the backing.