Shades of gray

I've never been able to remember how to spell the word that refers to the color range between black and white - is it gray or grey ? So I looked it up, and according to the sometimes trusted Wikipedia:

Grey became the established British spelling in the 20th century, and it is but a minor variant in American English, according to dictionaries. Canadians tend to prefer grey. The non-cognate greyhound was never grayhound. Both Grey and Gray are found in proper names everywhere in the English-speaking world. Americans tend to use "gray" in reference to the color and "grey" as the adjective.

So now we all know.