I'm dazzled by all this scholarly research, and charmed that one of the early sources of this song is right next door in VT (I've got to get me a copy of the Helen Hartness Flanders book- I get it out of the local state college library and renew it for months at time!)
I just want to add that this is just about THE favorite song of the local 5-7 year olds! When we sing it together they love to try to "stump" me- they try to think of color words that I can'f find a rhyme to (still working on "turquise" and "magenta...")