It’s not just green. I’ve seen it several times, and it’s not like any other cloud. Roiling, boiling, and it looks like an old bruise. Green, but with slight yellowish/purple gray tints.
That sounds ridiulous. You really do have to see it. Just nasty, eerie, and very frightening.
You have to see it, and you have to hear the racket—like a freight train roaring by right next to your ear. It’s all kind of magnificent, too—