Appointments on your calendar appear in different shades, depending on how the appointment is shown:
Busy. The appointment displays as gray.
Free. The appointment displays as white.
Out of the Office. The appointment displays as dark gray.
Tentative. The appointment displays as gray with white and gray stripes on the side.
To change an appointment’s Show Appointment As status:
Click Actions > Show Appointment As, and then select Busy, Free, Out of the Office, or Tentative.