So that plugin isn’t just for adding social icons. It will also do what you need. Let me know.
So for the nav buttons this CSS:
@media (min-width: 769px) {
.main-navigation .main-nav ul li a {
border-radius: 20px;
background-color: rgba(255,255,255,0.85); /* Change color for menu buttons */
margin-right: 2px;
}
.main-navigation {
background-color: transparent;
}
}
It overrides the static menu item colors set in the Customizer, the current and hover colors still apply though. Just a note, the nav doesn’t have a lot of room to breath. So increasing the margin (gap) between buttons will cause the menu to drop below the site logo.