To achieve your goal, you should edit the template of GridViewRow
element and delete the invalid visual state (RowInvalid). You can consider Using Implicit Styles. In that case, you can find the current template of GridViewRow and directly modify it in the respective Telerik.Windows.Controls.GridView.xaml file located in Themes.Implicit folder under the particular Theme you use. You should change it as per your specific requirements.
I hope this helps.