Man 1 will shout first...Suppose if Man1 will not shout then Man 2 surely shout.

Reason:

Man1 can see the other two criminals hats. If the hats are same color then he told his hat is opposite color of remaining two hats. So he shout first.

If Man1 not shout means that the color of hats (Man2,Man3) is different. So Man2 see the color of Man3 hat and he told the opposite color of Man3 hat is his hat.

-----------------------
suresh