Notifications menu colour problem

Ref: https://moodle.org/mod/forum/discuss.php?d=423596

#header2 overides body colours which then conflicts with the nature of .content-item-container .content-link and yet .popover-region-container should not really have a background colour defined (might be Boost too) and both should really follow .dropdown-menu in Bootstrap but their colours are in SCSS so therefore, should Adaptable generate more from there insead of CSS overrides (i.e. Apply / override SCSS vars) instead of even more selector bloat?

To replicate, find a notification id in the 'notifications' table and then have that id as a record in the 'message_popup_notifications' table, then the notification will be 'unread'.