You can add tags to your google calendar with this extension
This extension will arrow you to add colored tags to Google Calendar. By default, the separator is set as : (colon). Then, if you enter the name of the event, such as "Study:English:Vocabulary", the study and English in front of the colon will be recognized as tags and the background color will change.The background color is determined by the color of the calendar. You can also click on the extension's logo to open the settings screen. Here you can change two settings, one is the separator.By default, it is : (colon) but you can change it into any character you want. The other is , you can decide whether you remove the spaces in the appointment name or not.If you check the checkbox to the left of "Remove space", if you have a schedule called "Study: English: Vocabulary", it will automatically change the name to "Study:English:Vocabulary". If there is a space in the name of the event, the space will be included in the tag and the design will be disappointing. Also, under "Current Separator", you can see the character that is currently specified as the separator.