Slightly Scarlet  (1956) DVD starring John Payne, Rhonda Fleming, Arlene Dahl

Adapted from James M. Cain's novel Love's Lovely Counterfeit.
It is the story of a gangster working for a powerful gangster who is fighting to retain control of the city's criminal activities when an honest mayoral candidate launches a strong anti-crime campaign.
In order to derail the candidates career the gangster assigns one of his men to find dirt in the him. However, during the investigation the man falls in love in love with the candidate's beautiful red-headed secretary....

A nice film. A film noir, but in colour.