Navigation Bar

Hello
I was wondering if I am able to change the background on part of the navigation bar. I have attached two photos. The one labeled white shows the navigation bar with white background and the black one with black back ground. My question is this – If you look t the picture with the black background you will see where the menu is. I would like mynavigation bar to be black but I would like what is below the line – the menu Home About Us etc. to be white. Is that possible?