Okay, just thinking aloud, so you're safe to click it:
I'm thinking it must be a combination of probabilities and games theory. Which means that the fact that no one got away yet is a clue in itself.
What is the probability of each person being either blue or green? As it is random, I would have thought it's 50%. But in actual fact, it's 55% for blue, 45% for green. Is it because the numbers are relatively small, or is this the actual probability of each colour?
I tried to think by starting small. So you are inside the prison and the only other person is blue. What do you think about yourself? When one more comes along, how does the probability change? Not sure.
We have two groups of people with different views. Greens all see the same things as each other, so what one green does, every green does, as they are all so bright and clever. Same goes for blues. I'm not yet sure if the 100th person is in a different category or not. I feel he must be, but can't yet explain it.
Now there is a speech in both versions, that seems to reveal nothing new. But it must reveal something. Facts: there are greens and there are blues, you are 100, it's afternoon. Nothing new, right? Did the 100th person come before noon? So is the fact that no one left yet significant?
There is a question about when
someone will get out. So I'm guessing there must be a test period, like wait one day, and when no one does something, you deduce something. All too general to help anyone, but well....
See? Not really a spoiler at all, just random thoughts that probably add nothing.