Having a problem with containers

Hi,

I'm very new to GP. Trying to change my site over to a GP design this weekend and I've encountered a few teething issues. This is one issue that I haven't been able to work out yet for myself.

I'm using sections.

The first section is white background but I want the inner box full width.
The second section has a colored background, but I want the inner box to be contained.
I originally set up the first section with a contained inner box. When I changed it to full-width the color from the second section also appears in the first section. When I change the first section back to the contained inner box, the color goes back to white.

How do I get the first section to be full width without the color from the section below affecting it?

I have another page where I've used a similar design with the sections and had no issues at all, but this particular page doesn't seem to like me.