CSS to change nav bar background menu color

What is the correct CSS code to change the background color of the nav bar menu in Calumma theme? I am trying to help someone with their site, and while I was able to figure out the correct coding for the header bar (note: not yet live, just in draft until approved) I have not been able to figure out what specific CSS terms are used to change the navigation menu color on all pages. Yes, I used the code inspector, and I have tried all of these unsuccessfully – they did not change the nav bar menu color:
.site-navigation
.main-navigation
.menu-menu-1-container
.primary-menu
.nav-menu
Example – one of many experiments that did not work:
.site-navigation { background-color: #005587;
}