Can't change submenu attributes for mobile site

I’ve been struggling to help a customer adjust either the background color or the font color of a submenu item. I’m new to Beaver Builder, so possilby I am not putting the CSS in the right place.

The site is at, it is when I am viewing as a mobile width, and is the submenu under “Story”. I get grey text on grey background.

Can someone help me to either change the font color to white or the background of the submenu to white?

I’m trying to follow these steps and putting the code into both the style.css of the child theme files or Global Settings in BB, but not working.

/* Story SubMenu > SubMenu */
.fl-page-nav .menu-item-16137 .sub-menu .sub-menu {
    background: #ffffff;
.fl-page-nav .menu-item-16137 .sub-menu .sub-menu li a {
  color: #FFF;
.fl-page-nav .menu-item-16137 .sub-menu .sub-menu li a:hover {
  color: #FFF;

Any advice or suggestions on how to get this to work?