What could I be?

I wasn't able to get a picture, but I saw a small (warbler like) bird that was a light gray (not dark like a dark-eyed junco, for example) and had yellow on the bottom side of the tail.

I think the underpart/belly was a lightish yellow? I wasn't able to get a great look at it, but I distinctly remember seeing yellow under the tail, a patch on the end of the feather in a couple of spots (at least...it moved around so much I'm not sure!).

Any ideas on what it could be so I can narrow down my search? I'm in northwest Vermont along woods.

Check female American Redstart

Resin