Open XLSX in read-only that has print ranges defined, save as ODS, go to Format:Print Ranges:Remove and background color of sheet turns gray. You cannot remove the color by setting background to None.
You are likely in "Page Break Preview". There it is the desired behavior to show areas, which are not printed, with darker background. Switch to "Normal" in menu "View".
Will double-check, thought I was out of PageBreakPreview....