Thank you for the question.
When you are creating your own theme for the DocumentPresenter, please note that you should create a theme for RadTabStrip control as well, since the properties for the tabs are taken from this theme. I am attaching a sample project which demonstrates the approach. The ThemeName
of the themes should be the same.
In short, your task is to set the colors for the tabs in the RadTabStrip theme. I am attaching a sample project to demonstrate the approach. If you need additional assistance, feel free to contact me.
the Telerik team