Hello, @Andrés,
1. Please copy and paste the below-given CSS code to XStore >> Theme Settings >> Theme Custom CSS >> Global CSS and check back to your site after removing the browser cache.
.item-design-mega-menu .nav-sublist-dropdown ul li#menu-item-9381 a, .item-design-mega-menu .nav-sublist-dropdown ul li#menu-item-9369 a {
font-weight: 900 !important;
opacity: 1 !important;
text-transform: uppercase !important;
}
.et_b_header-menu.et_element-top-level .item-design-mega-menu .nav-sublist-dropdown .menu-item-9368.item-level-1>a, .et_b_header-menu.et_element-top-level .item-design-mega-menu .nav-sublist-dropdown .menu-item-9378.item-level-1>a{
font-weight: 900 !important;
opacity: 1 !important;
}
Please watch this video here: https://www.veed.io/view/e78554c0-d991-4942-b2ac-674194740518?sharingWidget=true
2. You have to translate/change it into the Core plugin language file, Please watch this video I have captured for you: https://www.veed.io/view/3e051712-3d98-4418-bcae-865cc7c34883?sharingWidget=true
3. I have just checked your site now on my personal mobile phone and the promo section background color is working perfectly fine, please see this screenshot: https://postimg.cc/NK99tC40 so it must be the cache issue at your end nothing else, please try to clear the cache and cookies and check back.
Regards 8Themes Team.