Each Designer Layout has its own document window. When these windows are maximized, as is usually the case, the front-most window covers the entire screen, or program window, so that none of the other drawing windows can be seen. This can be changed using the commands under the Window menu.
Cascade Windows and Tile Windows commands both show all the drawing windows, the former by overlapping them, the latter by dividing up the program window.
The background color of any layout can be changed using the Background Color command under the View menu.