White ribbon in MS Office applications in Tahoe 26.1

Hi,

since my update to Tahoe I have issues with the visibility of the icons in my MS office applications.

I added a screenshot from my PowerPoint, but it is an issue in Word and Excel as well. Above the ribbon is just a white stripe that should show you the safe button, for example. But the icons are white and so is the background of the ribbon. Only when you move the mouse over it, it becomes visible (poorly).

Anyone any ideas what I can do?

Thanks!