Navigation Background Colour

Hello, is there any code to change the background colour of the main navigation only?

I've created a mockup to illustrate what I mean. 

Thanks in advance. Regards, Jason

Can you share your website URL?

If I can find it I did help someone do exactly this last year...

Thanks, here you are:

https://piccolo-marlin-r22l.squarespace.com/home

Right, lets see where this get us, add to Custom CSS:

.header-layout-branding-center-nav-center .header-title-nav-wrapper {
    flex: 0 0 100%;
}
.header-layout-branding-center-nav-center .header-title-nav-wrapper .header-nav {
    background: #5f7315;
    padding: 12px 0px;
}
.header .header-announcement-bar-wrapper {
    padding-bottom: 0vw;
    padding-left: 0vw;
    padding-right: 0vw;
}

Let me know when you've got that code in and we'll see if any tweaks are needed.

Thank you Ziggy but there's a gap on the right hand side. 

https://piccolo-marlin-r22l.squarespace.com/

3 minutes ago, JCSMITH70 said:

Perfect Ziggy. Thank you very much for your help with this. Jason

Brilliant, would you be able to mark my post as the solution and give it a thumbs up? Thanks!