If I set a background colour on the master slide, that colour displays correctly in slideshow, but does not display in edit view. In edit view my slides still appear to have a white background. This is problematic when I want white or pale text on a dark background, as I cannot see the text in edit view.
This happened after moving to version 7.1.6.2, on windows 10. Previously on version 6(.?) backgrounds displayed as expected, in both edit and slideshow mode.
Are you using the ODF file formats?
Please upload an ODF type sample file here.
Workaround tip:
Downgrade to the LO 6.x.x version, and report the issue, if nobody reported it yet:
https://bugs.documentfoundation.org/
Choose menu Slide - Master Background.
Tested on LibreOffice 7.0.6.2 (x64), Windows 10.0.