Hello,
1. Try to use the code below as well:
.wd-dropdown-menu.wd-design-default .menu-item-has-children>a:after {
color: #333;
}
2. In this case, you can use our Layouts, e.g. for the specific category page you can create a Layout with the condition – https://prnt.sc/mi4MHVq5mrxM so in such a way you can customize different sidebars for each page.
Kind Regards