Definitely sun! Jendays are indeed more green on the back, but many jendays are actually more yellow in the face while being a more reddish-orange in the stomach area.
As far as behavior, well I've never bred conures before and none of mine have ever acted that way. However, I have seen videos of other conures displaying similar behavior and it was usually a "back off" kind of behavior.... like the bird sees something it doesn't like and puffs up to try to appear bigger and scarier.
I think this person is an idiot (and perhaps the owners as well, for allowing this), but you can see a more extreme version of a pissed off sun conure trying to go after a dog. There is the body swaying, wings out, tail feathers fanned some and beak open.
[ame="https://www.youtube.com/watch?v=ZkyzOttV2ic"]ANGRY CONURE! - YouTube[/ame]
Considering the age of the sun conure at your work, I highly doubt it's hormones but rather maybe he saw something he didn't like?