I have no idea what post (from when) you are referring to, or if it is me you are referencing. If it's something that you think I wrote then I would at least appreciate the courtesy of a correctly placed apostrophe. Sorry, but seeing "Iron's" is a major pet peeve. Given that I've seen Gray Flycatchers with green backs, I doubt that I would have written that they don't have green backs.
It interested me to see Iron's post that Gray Flycather would not show a greenish back. How about plain gray? Years ago on October 10 at Thornton Creek, long before there was good info regarding empids, and long before I developed such minimal expertise as I now have in identifying them, I saw one which was plain mouse gray above and white with no hint of yellow below, only a bit of a gray vest broken in the center by white. It had a pretty obvious eye-ring. Otherwise I saw no other significant field marks, and I never saw the bird move its tail. I wrote it off at the time as empid sp., but I'm wondering these many years later what comments might be forthcoming from others concerning an empid in such plumage.