I'm reading Salinger's "Ocean Full Of Bowling Balls" and came across the "blue card". I wonder what that means in that context. I found that "blue card" is currently used for immigrant agricultural workers, but couldn't be sure that they are related. It sounds more like it's related to sports somehow (baseball?) but I want to be sure. Any ideas?
"Hey Red, where’dja get that red hair?"
Kenneth turned around to look at the man, and said:
"A guy gave it to me on the road."
That nearly killed the guy. He was bald as a pear. "A guy gave it to you on the road, eh?" he said. "Think he could fix me up?"
"Sure," Kenneth said. "You gotta give him a blue card, though. Last year’s. He won’t take this year’s."
That really killed the guy. "Gotta give him a blue card, eh?" he asked, shaking.
"Yeah. Last year’s." Kenneth told him.
The fat man shook on as he turned back to his newspaper; and after that he looked over at our table frequently, as though he had pulled up a chair.
Full context can be found here.