Within Teamwork Projects, when you add an event to your calendar, you can choose to add it as a particular event type so that you can filter the calendar to show just events of that type.
Note: To add or edit event types, you will need to be a site administrator.
In the calendar view, click the options button on the right and choose Edit Event Types.
You will see a screen listing any of the event types that you have already added to your site. When you hover over each one you will see a link to delete it.
To edit an event, just click on its name. You will then be able to change the name, and the color associated with the event.
You can also create new event types, by clicking the Add new event type link at the bottom of the Event Types modal to create a new event type.
Click the 'Finish' button in the lower right when you are happy with your event types.
For more information, see: Creating an event in the calendar