The blue font LIbre uses when you go to save, it is totally illegible on my computer. I need to turn it off.
What is your OS and LibreOffice version? I’m guessing MacOS of some sort?
Are you referring to the blue background that highlights the suggested filename? If so, just press the right-arrow key and the blue highlighting will disappear. If not, please answer the request for more information asked above by @robleyd.