Noir: my favorite genre. Here's some color noirs I don't think have lost anything for not being in B&W: Leave Her to Heaven; Black Widow (1954); Blood Simple; Le Samouraï; Chinatown; Body Heat; Femme Fatale (2002); The Last Seduction; Thief (1981); Basic Instinct; After Dark, My Sweet.

My favorite noir however is indeed B&W: Detour (1945). To me it is the quintessential noir film.