<telerik:RadGridView.RowStyle>
      <Style TargetType="telerik:GridViewRow">
          <Setter Property="Background" Value="{Binding RelativeSource={RelativeSource Mode=Self}, Path=IsPinned, Converter={StaticResource PinnedToBackgroundConverter}}"/>
      </Style>
  </telerik:RadGridView.RowStyle>

public class PinnedToBackgroundConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var isPinned = (bool)value;
        return isPinned ? Brushes.Green : Brushes.Transparent;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}