You could apply a label when you set up a meeting or appointment by selecting from the Label drop-down list as shown here.
Earlier we showed that Craig added a lunch appointment to Luca's calendar. He colored the appointment orange, so that it would stand out for Luca as an appointment that Craig created.
With Editor permissions for the boss's calendar, you can create appointments for your boss as easily as meeting requests. Appointments that you create just appear in the boss's calendar. That is, there's no indication that the appointment was created by you, the delegate. (The same is true for meetings once they're actually in the boss's calendar. Only meeting requests and acceptances say "on behalf of.")
You could use labels to color-code meetings and appointments that you create in someone else's calendar. Labels enable the other person to spot quickly all the items that were entered by you. You could create a label in the meeting or appointment form when you create the meeting or appointment (as shown in the picture), or you could label later. To label an appointment after it has been created, you would right-click it in the calendar, point to Label on the shortcut menu, and select a label.
Note Colored labels that you put in someone's calendar are visible only to you and that person.