You can set different background colors for each membership you created. Let see an example of, how to create membership and how to set background color for a membership.
Step 1: Administrator -> Components -> Jom Classifieds -> Membership -> Add new membership
General Settings => [tab] => Enter the membership name.
Advanced Settings => [tab] => Enter the membership class name as per your requirement.
Screenshot 1: After the class name was added
Similarly, create multiple memberships and set class name for each as above.
Step 2: Administrator -> Components -> Jom Classifieds -> Global Configuration -> Custom Style
Start with “div#jomclassifieds” , and add the class name with .(dot) as its prefix. Check below screenshot
Screenshot 2: The result will be displayed as in below screenshot