[Vaskez]

Heh, the rules of the riddle aren't strict enough cos you can come up with loads of dodgy schemes to save everyone except the man right at the back. The man at the back coughs before he says his answer if the man in front has a black hat and no cough if he has a white hat. Then he guesses his own colour so he might even escape, but the man in front will already know what colour hat he is wearing and he can communicate to the man in front of him and so on, up to the man at the front.