> This isn't really related to the poem.
>
> > ... Clouds turned the sky to grey ...
>
> I always write "grey," even though my teachers always try to correct it to "gray" on assignments and the computer's spell check refuses to accept the first spelling.

It's a British/American difference. "Grey" is the British spelling, and "gray" is the American spelling. You're right that the two different spellings seem to carry too different connotations. "Gray" doesn't seem boring to me, but "grey" does seem more interesting. And, for some reason, I associate "gray" with a darker shade than "grey." But as that is a personal perception, I would never presume that others view these spellings with the same connotations.

I use "gray" now, because I'm an American and when all else is equal, I should probably be consistent with the way I spell other words. But under some circumstances, I have an aesthetic preference for "grey," even if I don't indulge it.