Looking back through my old commands, I see this:

Selection.Range.HighlightColorIndex=wdNoHighlight

You could create a Microsoft Word macro, using that text, and assign a hot key combination to it.

You also could use an Advanced Scripting command, using the same language, with a reference to the Microsoft Word object library.

Disclaimer: I haven't used this command in quite a few years. I expect it still works, but no guarantees.