Tools - Marking Cells - Display

Ribbon bar. Select the Tools tab. Click Marked Cells and from the menu, select Display...

Classic menus. From the Tools - Marking Cells submenu, select Display (or click the toolbar button located on the Spreadsheet toolbar)...

...to toggle between applying/not applying the Marked Cells spreadsheet layout to marked cells in the spreadsheet. In this way, you can visually distinguish between the cases that are marked and cases that are not. See also: Format - Overview, Spreadsheet Layouts - Overview.