There are a number of theories of who they are:
.Some say they are dolphins in the future or past (inhabitants of Atlantis)
.They are our future selves coming back to save us from catastrophe or to get sperm and ovules to mix their race with ours because they are all clones.
.Some say they are co-operating with the US government to trade advanced technology for usage of humans for experimentation. eg. B2-bomber , Stealth Bomber. They just sprung up from nowhere.
I got abducted by the greys and they stole my sperm.
The Greys are from Atlantis.
Some believe Greys are of the same species of alien as Reptilian. This is debatable.
i'm not sure. it's the grey of cheating. it's between right and wrong.
Grey 2: Throw up the shocker!