Thank you for writing.
You most likely need an instance of the ApplicationBarIconButton class that can serve as a protoype for the other buttons in your application. Since the ApplicationBarIconButton is not a dependency object and therefore not a Control child, you will not be able to provide templates or styles.
By default the Text and IconUri properties are configurable, that is, have public setters so you should be able to dynamically change them.
In order for the buttons to be theme aware, you will need to stick to a certain set of best practices when creating custom icons.
The text color is not configurable, unfortunately, and automatically changes with the theme.
In order to circumvent the limitations described above you will have to implement the application bar from scratch which could theoretically be done with RadWindow (which provides hardware acceleration) or with the default Popup control.
the Telerik team
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