I would suggest to check the Metro theme for RadScheduleView, you can find it in your installation folder, usually it is C://Program Files/Telerik/RadControls for WPF Q3 2011 SP1/Themes/, click the Metro folder and drill down to ScheduleView.xaml file. Search in the file the following string:
<!-- TimeSlot decorations -->
There you can find the styles for the TimeSlots.
Hope this helps.
the Telerik team
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