I had a hard time finding everything in one place when I started trying to customize my navbar but after a ton of hunting with Firebug / Chrome's development tool I was successful.
Let me point out that you should really learn some CSS when doing this. At the bare minimum selectors and how they inherit. I've been writing CSS for 10+ years and I still learn something new about it everyday. Please please use tools like Firebug and or the browser development tool for inspecting elements. It's not only helpful for understanding the structure of the CSS but will save you tons of time.
Under NavBar I opted to use the Standard NavBar - Light Grey Theme and the Standard NavBar is my Main Nav.
Screenshot of my NavBar selection and how my customized navbar looks.