After playing around with the inspector and trying what was posted here, I noticed my problem is that I was trying to make this full-width, and that the wrapper container for the navigation does not go full width, but the Header wrapper does. Unfortunately I couldn’t figure out how to specify the color of the wrapper and the nav-container to work both at its standard placement and the sticky scroll of the menu at full screen width.
I think to be able to do this I would need to make a new container for the header or look in the CSS codex that might force full-width (like 100%).
However you both helped me figure out how to change the nav-bar within the margin. Thank you!