If your columns are auto-generated you may subscribe to the AutoGeneratingColumn event of RadGridView and set the HeaderCellStyle from there:
sender, GridViewAutoGeneratingColumnEventArgs e)
The style1 is an explicit style which resides within UserControl's ResourceCollection.
If you need any additional info do not hesitate to contact us!
All the best,
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>