This add-on causes two markup changes in of Google Calendar.
Event names containing a colon (:) will have the part before the colon being displayed as a colored tag that helps discerning different kinds of events without the need for creating dozens of calendars.
For example: "Tag: Event name" becomes "[Tag] Event name".
Event names ending with a question mark will be displayed in italic and transparent, as a kind of optional or yet to be confirmed event.
This extension now also works in the embedded version of Google Calendar (to the right of Gmail for example).
Google Calendar is a trademark of Google Inc.
Use of this trademark is subject to Google Permissions.