To change the background of an appointment you can double-click on the appointment and use the Background combo box in the EditAppointmentDialog. When you select an item from the comb box you should click the "Ok" button to apply the new style.
You can also change the Background manually using a code like this:
Appointment newAppointment = new Appointment();
newAppointment.Start = scheduler.ActiveView.StartDate.AddHours(1);
newAppointment.End = newAppointment.Start.AddHours(5);
newAppointment.Background = AppointmentBackground.PhoneCall;
If you need more help, please write us back.
the Telerik team