What is the difference between grey and gray? I've seen both used and I'm wondering which I should use when talking about the color. Why are there two spelling's for the same word and is there a difference in the meaning between the two?
They are two different spellings of the color gray/grey:
Gray and grey are different spellings of the same word, and both are used throughout the English-speaking world. But gray is more common in American English, while grey is more common in all the other main varieties of English. In the U.K., for instance, grey appears about twenty times for every instance of gray. In the U.S. the ratio is reversed.
Grey gained ascendancy in all varieties of English in the early 18th century, but its dominance as the preferred form was checked when American writers adopted gray about a century later
First off, "spelling's" should be "spellings" above. Second, there's no difference in meaning between "grey" and "gray"; there are just two different spellings of the same word. There are a lot of words like this in English. Usually, there are different spellings because different versions of English spell it differently, i.e. there are British and American spellings of words. I don't know whether this is the case with "grey" and "gray". I'm American and I have spelled this word both ways, but I usually spell it "grey" as I think it's a more common spelling. Does that mean that's how all Americans would spell it? No, I don't know. There are words that are clearly more of an American spelling than British:
color (American) / colour (British) / eon (American) / aeon (British) / canceled (American usually but not always) / cancelled (British) / edema (American) / oedema (British) / anesthetic (American) / anaesthetic (British) / apnea (American) / apnoea (British) / capitalize (American) / capitalise (British) / practice (verb) (American) / practise (verb) (British) / counselor (normally American) / counsellor (British) / center (American) / centre (British).
It's just the way it is because there are so many variants and dialects of English.