Change Primary Menu Color

Hi I’m trying to change the color of the primary menu. I’ve tried all the theme options, and I can only change the color of the topbar and the whole header, but I can’t seem to figure out how to change the color for the main menu.

website is at:

https://mojomojo.co

I just want a all black menu at the top of the screen (below the logo), just like the footer menu. Is there a specific option for this in the theme options? Or would I need to use some CSS code. I’ve also tried using some different CSS codes I pulled from sources online and inserting them into the custom CSS box to see how they affect the menu color, such as :

Tried this one:

.main-navigation {
background-color: #ffffff;
}

This one:

#nav {
background: #ffffff;
}

And this one:

nav#main a {
color: black;
font-weight: bold;
}

But none of them seem to change the color of the menu. Please help!