Is there one place I can change the background color (ie. background:#DDDDDD) for the entire theme. I notice when I change the color from default white in the overall style and config, it only effects the header and body regions, but not the sidebars or footers.

Just put your color hex code in the styling areas for the sidebars in the sidebar configuration area in the theme options.

to elaborate on Paulae answer, in a word NO. The theme allows you to control the color in hundreds of places. You could set all those locations to a background of transparent, then the body color would show thru, but there is no one place to do it.