Three people A,B,C are standing in a line so that C can see A and B, B can see A but not C, A cannot see anyone. There are 2 blue hats and 3 red hats and 1 hat is placed on each of them. Now when asked - Do you know the colour of your hat ? : C answered 'no' Then B was asked and he too said 'no'. Then A was asked and he said 'yes'. What is the colour of A's hat ? P.S. They can hear answer of each other.