I'd like to ask a question which is about an idiomatic phrase blue paint down there. I want to know what it means and in what way I can use it. Thank you.

Old Sally’s ankles kept bending in till they were practically on the ice. They not only looked stupid as hell, but they probably hurt like hell, too. I know mine did. Mine were killing me. We must’ve looked gorgeous. And what made it worse, there were at least a couple of hundred rubbernecks that didn’t have anything better to do than stand around and watch everybody falling all over themselves.

 “Do you want to get a table inside and have a drink or something?” I said to her.

 “That’s the most marvelous idea you’ve had all day,” she said.

 We took off our goddam skates and went inside this bar where you can get drinks and watch the skaters in just your stocking feet.

 The Catcher in the Rye

Jerome David Salinger