Full width background per block in Devlin?

Hi there! I'm trying to make sections that have differently coloured full width backgrounds. The content stays within the site-width but the background spans across the entire width. (like they do it with the footer here, but doing the same for content sections http://squarespace.com/templates/?q=devlin)

How can I achieve that? I have very little knowledge of code, so the more explanations the better :)

Any help would be much appreciated!

I'm looking for help with the same thing in the Five template. Best of luck!