You can configure a stylesheet in the Data Type configuration for your Tiptap editor. You can select any stylesheet found in the wwwroot/css folder. You can also reference these stylesheets on your MVC frontend:
Reference from the Docs:
Stylesheets
To apply custom styles to the Rich Text Editor, you can select from any existing stylesheets.
Stylesheets can be created in the Settings section. To learn more about this feature, see the Stylesheets in the Backoffice article.