Created attachment 201274 [details] libreoffice info, google sheet display, libreoffice display, the excel file used in display Only red color cells are shown clearly, others are difficult to see.
*** This bug has been marked as a duplicate of bug 166942 ***
While OP is on 25.2.4 release, need to install and apply from the Tools -> Options -> Appearance panel the 'Light Application Color' appearance theme. That will restore their OOXML spreadsheet to visible settings in the UI At 25.8.0 that theme is not required as a 'Use white document background' feature has been implemented and checked enabled by default.