Chanman, good theory. Considering his love of color symbolism in his films, I will watch The Happening again and pay attention to the yellow.

Yoda said:
So, the film may stop short of stating things outright, largely because Night doesn't like to do that sort of thing...but it's pretty clear that it's a) coming from the plants and b) spurred by the existence of nuclear power.
Yoda, you contradict yourself. You point out all these things that make it completely obvious, beyond a reasonable doubt, that it has to be the plants that caused the incident, yet you say M. Night doesn't like to be blunt in his symbolism.

If it really IS the plants, M. Night has lost all his subtle storytelling skills, because it's alluded to again and again and again in the movie that this is an environmental disaster and people are the problem.

So you can't have it either way. Either M. Night is subtle and there's something under the surface here, or he has bludgeoned us over the head with his political message. Either/or.