You weren't unclear.
ALL progs BG color can be specified in Start Menu and Taskbar > Start Menu > Left hand Side > More Programs Background > Extra Tab > All Progs list background color > Choose from list.
New app is a color if no image is specified but there is no control for it.. it pulls it from the skin colors as far as I know.. unless, the author has used an image for it, in which case you will need to replace the image or recolor it.
You can find it at Start Menu and Taskbar > Start Menu >Start Menu Popup menu > New Application item.
Make sure you have the treeview 'view' chosen in preferences to broowse thru the sections... altho I think it's only available in SKS Pro.