Change Background Colour of Whole Menu Div

I am trying to colour my whole menu block forcibly white. I can see all these colour options but they seem to only the various child, parent etc links, which is great, I just want to be able to force some custom css onto the div. I am poking around inside of the plugin but can’t see where the class is created for my particualar module.

I am really just looking to add the classe white to the parent div

I can’t provide a live site at the moment because it is hosted internally. I am more than happy to further clarify.

Thanks in advance.