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.