Elia Kazan made Gentleman's Agreement, which won Best Picture in 1948. It's a sort of overwrought melodrama about prejudice against Jewish people in upper class society. It stars Gregory Peck and Dorothy McGuire. The gist, if I remember correctly, is that Peck pretends to be Jewish for a period of some months as an experiment just to see how differently he's treated by the people he knows and works with. Things all turn out right in the end, after many complications from his fiancée and job, etc, etc.
Pinky, which Kazan made two years later has the same sort of conceit. An extremely light-skinned black woman (the very white Jeanne Crain) returns to her home in the rural South to her grandmother (Ethel Waters) after her white boyfriend proposes to her. This film is sort of about racism, but actually doesn't delve into issues of passing for white too much. It's more about... well actually I'm not too sure what it is about. More than anything, it's a middle-sized Southern melodrama about being who you really are and not pretending to be something you are not. Much wit and wisdom is dispensed by former plantation-owner Ethel Barrymore, who is Ethel Waters' best friend in the film. The racism and prejudice of white people in the South are taken for granted and are part of the film's backdrop, but Pinky isn't really a drama about race. It's the importance of values like honesty, family, duty and responsibility that are stressed.
I found it extremely hard to believe Jeanne Crain as a black woman, but her performance is really quite good and never offensive (at least to me). I've never much liked Jeanne Crain (neither did Joseph L. Mankiewicz, I'm told) but I rather liked her in this. She plays a rather off-putting character for most of the film and she never underplays it so that the audience will like her more. It's good work and she was nominated for an Oscar for her performance. The Academy didn't care for Pinky quite as much as it cared for Gentleman's Agreement, though. Agreement nabbed 8 nominations and 3 wins. Pinky wound up with only 3 nominations and it didn't win a thing.