Problem with the submenu

Hello, i have installed the JUX Mega Menu. This is fine. I have now a little problem.

The color of the submenu is not in full widht.
The first part (left) is grey, the rest is with....


Where is the setting in CSS for change this ? I try with STYLE.CSS and BLACKANDWITH.CSS

Thank you for help me. I try a lot of thinks in css... Nothing work...

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