If you are a member of a large number of groups, this method is the best choice for achieving a clear visual distinction. With it, you can view group events (for your Outlook groups) separately and overlay or turn them off at any time.
To set up a separate calendar view for a user group from Outlook, follow these steps:
Open Outlook in your browser.
Go to 'Groups' in the left pane menu and locate the group you want to add. Click on it and copy its email address.
Paste the email address here and enjoy the clear visual distinction.