Here is a detailed article
about the template structure of FilteringControl and all the other significant visual elements of RadGridView. In order to customize its template, you should extract its default template with expression Blend, apply your changes and propagate the new template through a style. You can use GridViewBoundColumnBase's FilteringControlStyle property to set the style to a particular column. On the other hand, if you are using our new implicit-styling mechanism, you can find the template in the merged XAML resource dictionaries and apply the changes there, without the need of any additional effort.
All the best,
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>