How to have background images scroll at different speed than foreground content?

I don’t know how to ask this question right without an example.

I’m looking at this site: http://www.astoriacassis.com/#

Scroll down quite a ways. You’ll see that as the content (text and images usually on white) moves up, different full screen images appear behind the content, always partially covered by the main content. These images are replaced as you new content scrolls up from below. I think this is very cool. :-)

I’m trying to figure out how to do something like this in Enfold. Color Sections?

Thanks for any insight.