Most of the color Mario Bava films, like Black Sabbath, Kill Baby Kill, and Lisa and the Devil. Also the quasi horror of Hercules In The Haunted World.

Let me also speak up for the two-color Technicolor horrors of Dr. X and Murders In The Wax Museum. The ghastly color is unlike most films, but so effective in evoking another world. Seek them out if you haven't seen them, even if they seem outside what you were looking for as rich color experiences.

A few other Hammer films to look out for are Curse of the Werewolf and Blood From The Mummy's Tomb.

Creepshow uses artificial colors to heighten scenes and make a bigger connection to the world of comics.