I am trying to reset my default font and cell background colors to black and white, respectively. They are now white and black.
I was creating a presentation when suddenly all the text - many pages, usually a title and outline per page - swapped foreground and background colors. It happened instantly and not in response to anything I did on purpose. Not only that, text in all new and newly opened saved documents is also reversed. The cell backgrounds are black and the text is white, except for cells with explicitly set colors, which appear with the colors I set. I have quit and restarted, and even rebooted. I have googled for hours and I find nothing relevant. Font and background colors in all other applications are normal. But, all LibreOffice documents types, including formulas, now are white-on-black. It has to be some global setting.
I’m on Version: 188.8.131.52 Build ID: 1:6.0.7-0ubuntu0.18.04.10.
What has happened, and how do I undo it?