I was forced to reinstall Office 365 to check performance issues.

Until now, I have been using dark mode, which I don't like, but the glare of regular mode is too much for me.
I want to set Office up so that everywhere within the app where Word displays as white, it is shown in light yellow.

Is there a step-by-step guide on how to do this?

Thank you, and have a good day!
Susan Flamingo

No, because it is not possible to customize the UI themes.

You can, of course, change the page color via the Design tab if the white page hurts your eyes, but that has its own drawbacks.