On the Add or Edit Service overlay, there is a field called Task Color:
Customize the selection in this field if you commonly use the Calendar in SA. This Task Color is only visible on the Calendar so you can view daily appointments easily by Service. This color is not visible on the Dispatch Board or Dispatch Calendar. If you are not in the practice of using the Calendar, you can simply leave this field as the default color.
For more information about viewing this Task Color on the Calendar, click here.