I suspect you’re changing the background color of something else on the page other than the Navigation Bar. The Navigation Bar stack has a section labeled “Bar” in which you’ll find the controls for the background color of the Nav Bar:
If you can send me a ZIP file containing your project file, or at the very least show me a screenshot of the window when you’re editing the color I can help out further if my above screenshot doesn’t help with clearing it up for you.
I was changing the Background color at the top of the information panel. That apparently controls the background color of something, but not the nav bar. As soon as I scrolled down to the bottom and found the Bar section, it worked fine.