How can I change the background for a specific cell?

I’m using OO4, the Pro version. I’d like to change the background color of a single cell in the document, is this possible?

I’ve tried highlighting all of the text in the cell and changing the background color in the Inspector, but that only changes the background for the text, not the whole cell. Apparently this was the way to do it in OmniOutliner 3 but I can’t get it to work in OmniOutliner 4.