A stranger walks into a bar, looks at the board, puts $5 down and asks for a pint. The barkeep asks if he wants the Stout or the Amber. The stranger asks for the Amber.

Another complete stranger comes in, looks at the board, puts $5 down and asks for a pint. The barkeep immediately pulls a pint of Amber.

How did the barkeep know what the second stranger wanted?