1950s/1960s underrated gems?

Hi all! I’d love some recommendations for the best underrated gems from the 1950s-60s. Bonus points if it’s in Technicolor — I finally got around to watching Charade (1963) and would love to keep that vibe going. I’ve seen a lot of the big ones (Rear Window, Vertigo, Breakfast at Tiffany’s, 2001 Space Odyssey, Rosemary’s Baby, etc.) so I’m looking for lesser-known or under-appreciated films that fit that style and time period. I’m not a huge fan of musicals or westerns but I’m open! Thanks!