This is what linguists technically refer to as, "stuff no one should really care much about."
1. Languages do not exist in and of themselves; they exist only insofar as people mutually comprehend them. There is no "out there" authority that can tell you what is correct in a language, only general consensus. Even dictionaries (barring some loonies like Daniel Webster) attempt to find the consensus and get their authority from the fact that what they put in is what everyone is already doing.
2. Although an odd spelling may cause a small hiccup in your reading, and slow you down, and that might be kind of annoying, both spellings of grey/gray are so common that you will undoubtedly understand what you are reading. Since the point of text is to communicate, it succeeds either way.
3. Writing is a sad representation of speech, as a charcoal drawing of a person is to an actual person. This is compounded by the fact that people start thinking it's "out there" somewhere and you need to get it right, so people keep spellings the same even as the way people talk changes, leading to silent letters and other weirdness. The idea that either one is "right" enough to make the other one invalid is giving a little too much credit to the written word. If you want to really try and do the word justice, the international phonetic alphabet is the foremost example of an attempt to capture the sound types used (if not tones and pauses) in virtually all human speech; in the IPA, the spelling of the word in question, at least for the time being, is "greɪ"
topic over
also I spell it gray because i live in america but the point is no one should care
Poll