From Kook Science

Greys (or Grays) is a popular namesake for a group of beings, so-called for the grey colouring of their skin or bodysuit. They are frequently described by contactees as diminutive, slim beings with comparatively large ovoid heads and enormous black eyes, otherwise lacking in features such as ears and noses, and have been attributed a dispassionate or malevolent character in contactee reporting and popular entertainment. Their first widely reported appearance is generally claimed to be the Betty and Barney Hill abduction of 1961.

The origin of these beings has been often described as extraterrestrial among contactees, though it has also been reported that they are of Earthly-origin, interdimensional-origin, or represent evolved future generations of humanity, acting as chrononauts.