Watch Plastic Saints (1968) Official Trailer

"While still a student at Yale University, Nick Doob made a series of short works that launched his career in film. One was Plastic Saints, in which Doob took black-and-white footage of a demonstration in Washington DC that he and four fellow students attended, and intercut it with color paint-on-film loops, all set to a recording of “When the Saints Go Marching In.”" - Moving Image Archiving News