Amanda was suspicious. Who was this stranger kid? And what was he doing in the East End, where almost all the kids were black? And why was he saying that? (3.3)
The Cobras were standing at Hector Street. Hector Street was the boundary between the East and West Ends. Or, to put it another way, between the blacks and whites. Not that you never saw a white in the East End or a black in the West End. People did cross the line now and then, especially if they were adults, and it was daylight.
But nighttime, forget it. And if you were a kid, day or night, forget it. Unless you had business on the other side, such as a sports team or school. But don't be just strolling along, as if you belonged there, as if you weren't afraid, as if you didn't even notice you were a different color from everybody around you. (9.16-17)
Dead silence along the street. The kid had done the unthinkable, he had chomped on one of Mars's own bars. Not only that, but white kids just didn't put their mouths where black kids had had theirs, be it soda bottles, spoons, or candy bars. And the kid hadn't even gone for the unused end; he had chomped right over Mars Bar's own bite marks. (10.33)