Menu Bar Background Color

Terrific theme which I have been able to tweak so it looks great for our site. One minor glitch yet and for the life of me, I can not find either the image or css that controls it. Basically, it is the color of the menu bar to the left and right of my drop down buttons. I have attached an image to show my issue, but it is splitting the far left/right side of the menu into black and grey. If anyone could point me to the right spot to customize this so I can make it all black, it would be greatly appreciated.

Many thanks in advance,
rb