hmm.. eastern colorado? I'm not sure. If it were east, south, or north of you I'd say it was some kind of garter snake, but I know nothing about that area of the US(or anything west of you either)

Sure is a cute little guy

As much as I want to laugh at your neighbor for freaking over a little snake, at least she didn't try to pick it up without knowing whether or not it was poisonous. A neighbor of mine when I lived in Louisiana got bit by a 3-inch long 1 cm(or skinner) wide baby copperhead that way, thought it was a little garter or something.