They dont see the same spectrum of light as we do. Taking them outside is not the same for you and I and as it is for an iguana. When you take them outside they freak out because theyre being exposed to what to them is a totally different extreme to their senses.

Its not only a Rhino iguana reaction. I've hatched panther chameleons and when raised together indoors they get along fine. Take that same group outside and they act like they don't recognize each other and pose defensively.

In my opinion the world they see visually is not exactly the same spectrum you and I experience.