Also rum is cheap compared to beer. Four guys will split a fifth of rum with 2 liters of Coca-cola and play dominoes for a couple hours. Dominos is a great way to relax-- it's loud, it fast and you have to keep track of what is going on so you try not to get too drunk.
Many Dominicans don't hang out at bars. They can be at the local 8'x12' colmado and in front of the store will be the domino table and the guys buy the booze at retail price, not bar price. For the price of a shot in the US, they can get a whole bottle.
I used to play dominos on the beach once in a while with the locals. When I was playing my first games, I bought a small bottle of rum for the table and they let me play with a guy behind me giving me tips. When I came back a day or two later, they had a BIG bottle of rum and shared it with me. That's the kind thing I like to remember from the DR.
The guy in the blue shirt has his arm up in an aggressive pose. He is basically letting the other players know that he knows what they have in their hands and he knows what they are going to play and he is in control of the game.