How to Change Navigation menu background color using css

I want to change Nav menu background color using the css file because the changes I make don't appear using the design at the admin background.
I need help locating this file.

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micrdy replied on at Permalink Reply
You want to change the backround color of the autonav block? Why not just using css and override these values?
bookerzm replied on at Permalink Reply
Yea. I want to know the path to the css file.
jasteele12 replied on at Permalink Reply
Turn off concrete5 caching, view the source of your page.

It's going to be something like themes/theme_path/main.css or packages/package_name/themes/theme_path/main.css