VerticalSliceModifier Only Showing With White Background - How Do I Change This?

Hello,

When adding a VerticalSliceModifier to a chart, the axis label background color always shows up white, instead of the stroke color like in the examples. How can I change this property?

private void OnCreateSliceClick(object sender, RoutedEventArgs e)
{
       MouseButtonEventHandler mouseClick = null;
        mouseClick = (s, arg) =>
          {
                    this.MouseLeftButtonUp -= mouseClick;

                    var mousePoint = arg.GetPosition((UIElement)this.sciStripChart.GridLinesPanel).X;

                    var slice = new VerticalLineAnnotation()
                    {
                        X1 = this.sciStripChart.XAxis.GetDataValue(mousePoint),
                        Style = (Style)Resources["sliceStyle"]
                    };

                   sliceModifier.VerticalLines.Add(slice);
         };

         this.MouseLeftButtonUp += mouseClick;

}

  <s:SciChartSurface.ChartModifier>
             <s:ModifierGroup>
                        <s:VerticalSliceModifier Name="sliceModifier"/>
              </s:ModifierGroup>
  </s:SciChartSurface.ChartModifier>


<Style x:Key="sliceStyle" TargetType="s:VerticalLineAnnotation">
            <Setter Property="ShowLabel" Value="True"/>
            <Setter Property="Stroke" Value="#427EF6"/>
            <Setter Property="IsEditable" Value="True"/>
            <Setter Property="LabelPlacement" Value="Axis"/>                          
</Style>