Most of the time, we need to find controls under at RowDataBound event of GridView control to do some important functionality.
For example, Show/Hide the control, change the color of the control, bind some javascript function with the control etc.
So below is the code to skip the header in the RowDataBound event of GridView
if (e.Row.RowType == DataControlRowType.DataRow){
CheckBox chkBox = (CheckBox)e.Row.FindControl("checkbox1");
chkBox.BackColor = System.Drawing.Color.Red;
}