The 250 Quintessential Noir Films listing contains 241 films that all contain three key ingredients.
They were all produced in the United States
They were all shot in black-and-white
They were all produced between 1940 to 1959.
The nine films, that have been included, that exclude at least one of these key ingredients are two Non-American-produced noir (The Third Man and Mr. Arkadin), four colour noir films (Leave Her to Heaven, Niagara, Party Girl and Slightly Scarlet), and three films from the early 1960s (Cape Fear, Underworld, U.S.A. and The Naked Kiss).
List has been curated by Bill Georgaris on They Shoot Pictures, Don't They?