You can define categories for appointments to change the background color of their badges in the Calendar. See Schedule settings: Categories for more information about category configuration.
Define appointment categories
To define a category use one of the following methods.
Right-click an appointment badge in the Calendar, go to Set a category and select the category.
From the Appointment window, go to the second Show as drop-down menu and select the category.
Remove appointment categories
To remove the category, from the Appointment window, go to the second Show as drop-down menu and select Clear.