Hi Mikiya Sato,
In order to change this
Border , you can edit the
Control Template of the
RadTabControl. Then you can change the Borders inside the
LayoutTransformControl named
HeaderDockedElement. Please try the attached project where the described approach is implemented and let me know if it satisfies you completely.
Kind regards,
Petar Mladenov
the Telerik team
Browse the
videos here>> to help you get started with RadControls for Silverlight