I suspect the image of the nymph is also Chlorochroa.

I spent about 10 hours searching the net, trying to find an image identical to that nymph. I had no luck. None had the obvious red/orange knees, though some did have slight touches of red/orange on the knees. However, none at all had the red/orange centers to the black markings bordering the abdomen, and though some had similar dorsal patterns, none were actually close enough to consider an identical match.

It would seem that the best way to determine what a nymph grows into is to raise them into adulthood. This next season, I will try to do just that. Any pointers on how to best do it? I was thinking quart mason jars with a porous cloth lid containing one nymph each and a cutting from the plant I find it on - and don't let it bake in the sun. If the project works out, I'll submit my results to BugGuide.