Highlighting Effect Behind White Text

I'm using an InDesign template, running InDesign 2020.

I'm adding a new text block to the project. Everything functions normally until I try to change the text to white. Then I get a blue background, like the highlighting function in Word. I can't find this under any of my text block panel settings. When I switch back to black text, it's transparent again. As you can see, it's not filling the whole block either.

I've searched other community questions and can't find anything about this particular issue. It's not a missing font, either. This is Minion Pro, and it's the same story for any other font I switch to.