I expect Elements will devise a more streamline way to apply a background colour to the body soon. Right now, there are a few ways to skin this cat, but one of my favourites :
Works if you use a container as the outer most element of the page.
Select the container.
Set its background colour (the faux body background).
Content layout > align top
Would be really nice if this was in its self a component (locked in place) that when clicked revealed the body settings in the settings column, just as other components do. There’s a few settings that could be included as well as background.