Suppose instead of being 900 brown eyed people there are X brown eyed people.
Suppose X is one, then the brown eyed person appears to be stuck, all the blue eyed people are dead so he knows he doesn't have blue eyes, but he can't determine what colour his eyes are (are they brown?, are they green?).
If X is two then we're left with two people after all the blues are dead. Each one can see a brown eyed person, but again, this doesn't help them determine what colour their own eyes are. Again, why can they not be green?
The case for X>2 seems similar to the case for X=2, there's no magical point at which they can suddenly all say 'I don't have green eyes, I must have brown eyes'
With all respect, I think you are underestimating the problem. :)
Suppose X is one, then the brown eyed person appears to be stuck, all the blue eyed people are dead so he knows he doesn't have blue eyes, but he can't determine what colour his eyes are (are they brown?, are they green?).
If X is two then we're left with two people after all the blues are dead. Each one can see a brown eyed person, but again, this doesn't help them determine what colour their own eyes are. Again, why can they not be green?
The case for X>2 seems similar to the case for X=2, there's no magical point at which they can suddenly all say 'I don't have green eyes, I must have brown eyes'
With all respect, I think you are underestimating the problem. :)