CAR 54, WHERE ARE YOU? was filmed (in black-&-white) on location in Brooklyn
and the Bronx using patrol cars painted red and white so that passersby would
not confuse them with real New York City police cars painted green and white.

Car 54 was based at the old Biograph Studios at 807 E. 175th St., in the Bronx, New York City (a very old and large studio complex, that was abandoned in the 1970s and burned around 1980). Much of the location filming was done in the Tremont section of the Bronx using red and white cars as you mentioned. Incidently, some episodes of "Naked City" were shot at this studio too.