We'll create fresh WordPress site with Bring Back Admin Menu Separators installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugins just adds some CSS to make the admin menu separators visible again, since a lot of people are confused with no visual separation in the new WordPress Admin Design.
Works for all default color styles.
If you want to change the colors of the separators you can copy the php code from the plugin file and add it to your themes functions.php.