guy 1: hey you see that guy over there?  guy 2: yeah what about him?  guy 1: he's a blue jew  guy 2: what? he's jewish?
someone who is jewish but doesn't look like it
"guy 1: hey you see that guy over there?  guy 2: yeah what about him?  guy 1: he's a blue jew  guy 2: what? he's jewish?" What is the definition of "blue jew"?