You can use the ribbon command View | group Windows | Dark document 
to switch the worksheets from their usual white to a dark display.
Tip: You can also easily add this button to the Quick access toolbar. To do so, click on the icon 
on the far right of the Quick access toolbar. Select Add/remove buttons and enable Dark document.
If you click on this command once, the worksheets will be displayed in dark mode. If you click on this command again, the worksheets will be displayed in white again.
Switching this display has no effect on the printout of the document.