[Theme: Vintage Camera]

If this change is not apparent through the dashboard, you should set up a Child Theme or use a Custom CSS plugin to implement your changes, rather than editing and modifying the theme’s files.
Does that theme come with an area in the dashboard named something like, ‘Custom CSS’ ?

Have you a link to the webpage at-hand?

If I’m understanding correctly, does this CSS replicate your needs;

.navbar {
 background-color: #000;
}

Can you try adding this in the Custom CSS section?

In that instance, a Child Theme is imminent as you’ll need to add the same function that calls the navigation from the footer file, into the header file.

Have you a Child Theme?