I spell it grey. The reason why there is no "e" (or "a," for that matter) in my user name is because I have spent over 30 years in Law Enforcement Public Safety Communications, and the appropriate NCIC abbreviation for the color is "gry." (The abbreviations for purple and orange are, respectively, PLE and ONG, in case anybody was wondering. Betcha nobody was, though....)
Anyway, as my eyes are grey, I've always used gryeyes.
Anyway, as my eyes are grey, I've always used gryeyes.