Removing the border around my custom menu

I have implemented this plugin and began using it to build my new website. I am trying to remove the border around the menu, so that it blends in with the rest of the page.

Any ideas how I can edit the code around the border so it appears to be the same color (white) as the rest of the area?

Here’s an example page.

https://www.ads-software.com/plugins/jquery-vertical-mega-menu/