Hi ambercromby,
You can use the following CSS code:
.t4-megamenu .dropdown-menu {
background: #0000cd;
}
.t4-megamenu .dropdown-menu li > a:hover, .t4-megamenu .dropdown-menu li > a:focus, .t4-megamenu .dropdown-menu li > a:active, .t4-megamenu .dropdown-menu li > .nav-link:hover, .t4-megamenu .dropdown-menu li > .nav-link:focus, .t4-megamenu .dropdown-menu li > .nav-link:active, .t4-megamenu .dropdown-menu li .dropdown-item:hover, .t4-megamenu .dropdown-menu li .dropdown-item:focus, .t4-megamenu .dropdown-menu li .dropdown-item:active {
background: #0000cd;
}
.t4-offcanvas {
background: brown;
}
.t4-offcanvas .t4-off-canvas-body .navbar .nav-link, .t4-offcanvas .t4-off-canvas-body .navbar .separator {
color: #fff;
}
.t4-offcanvas .t4-off-canvas-body .navbar .nav-item.active > .nav-link, .t4-offcanvas .t4-off-canvas-body .navbar .nav-item.active > .separator {
color: #999;
}
.t4-offcanvas .t4-off-canvas-body .navbar .dropdown-menu {
background: brown;
}
.t4-offcanvas .t4-off-canvas-body .navbar .dropdown-menu .dropdown-item, .t4-offcanvas .t4-off-canvas-body .navbar .dropdown-menu .nav-link {
color: #fff;
}