To me, grey looks greyer. The Middle English form (AHD) was grei. And the British, who see a lot of it nearly every day, prefer grey. OED points out, however, that Dr. Johnson's dictionary spelled it gray, that grey is "phonetically ambiguous (I suppose it could be mispronounced to rhyme with key, by someone unfamiliar with bey, fey, hey, lei, obey, prey, they, threy, whey, and oy vey), and that there are other linguistic arguments for the -ay spelling.
OED also notes that some nineteenth-century printers asserted that grey and gray were not quite the same color: the former being only a mixture of black and white, while the latter might be lighter or warmer - or "any broken color of a cool hue," according to Field's Chromotography (1885), which insisted that "the distinction between grey and gray should be carefully observed." A voice in the wilderness.
February 20, 2009
Wordplay in Gray February
Of wordplay there is no end and Roy Blount Jr. brings the enthusiasm of an amateur in his tasty "Alphabet Juice". Note with what relish he handles the long-standing controversy between gray and grey: