Subway riders in New York navigate by a combination of rote and conditioned reflexes — making the correct turns, choosing the right platform and (except on rare, embarrassing occasions) jumping on the right train without much thought.

They also rely on a poetic sense of color: Broadway lines, for example, are red; the Eighth Avenue lines are blue.

Except when they are not.

At the Columbus Circle station on Sunday, a sign on a downtown platform had mixed up the colors of the B and C lines; the B wore the Eighth Avenue blue and the C was dressed in a shock of orange.

Because the signs directly above the tracks had the correct colors, confusion, let alone chaos, was not readily apparent. But quizzing subway riders about the sign did prove an interesting test of observational skills, as well as something more ineffable about how much people cared about the details of their environment.