Menu

GeneratePress: Menu Underline Effects

@media (min-width: 769px) {
    .main-navigation .menu > .menu-item > a::after {
        content: "";
        position: absolute;
        right: 0;
        left: 50%;
        bottom: 15px;
        -webkit-transform: translateX(-50%);
        transform: translateX(-50%);
        display: block;
        width: 0;
        height: 2px;
        background-color: currentColor;
        transition: 0.3s width ease;
    }
    .main-navigation .menu > .menu-item.current-menu-item > a::after,
    .main-navigation .menu > .menu-item.current-menu-ancestor > a::after,
    .main-navigation .menu > .menu-item > a:hover::after {
        width: 50%;
    }
}

GeneratePress Divider between Menu Items

@media (min-width: 769px) {
    .main-navigation .main-nav > ul > li:not(:last-child) {
        position: relative;
    }

    .main-navigation .main-nav > ul > li:not(:first-child) > a:after {
        content: " \007C";
        display: block;
        position: absolute;
        left: 0;
        top: 0;
        font-size: 10px;
    }
}

GP: Sticky Navi colors

Background: 
.main-navigation.navigation-clone {
  background-color: rgba(74,94,155,0.7);
}
Menu Items 
.main-navigation.navigation-stick .main-nav ul li a {
  color: #000000;
}

GP: Trigger specific Menu Item

Dem Menu Item die class
nav-button 
geben.

@media (min-width:769px) {
  .main-navigation .main-nav ul li.nav-button a {
    background-color: #ffffff;
    border: 2px solid #000000;
    color: #000000;
    line-height: 35px; /*this number will likely need to be adjusted*/
  }
}