I have the WPFToolKit-Chart control which contains date and hours worked values. I want to change the color of column according to values. For example, I want to make the color orange when it exceeds working hours like the picture below.

I think it will be done using Trigger, but I could not complete the fiction.

This is my XAML markup:

    xmlns:chartingToolkit="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"

    <chartingToolkit:Chart Name="chart1"
                           Title="Availability"
                           VerticalAlignment="Stretch">
   
    <chartingToolkit:Chart.Series>
                <chartingToolkit:ColumnSeries  ItemsSource="{Binding MyGraph}"
                                   IndependentValuePath="Key"
                                   DependentValuePath="Value">

       <chartingToolkit:ColumnSeries.DataPointStyle>
           <Style TargetType="chartingToolkit:ColumnDataPoint">
               <Setter Property="Background" Value="#00777F"/>
               <Style.Triggers>
                   <Trigger Property=" Value > 8" Value="true"> <!--I need to adjust this part.-->
                       <Setter Property="Background" Value="Orange" />
                   </Trigger>
               </Style.Triggers>
           </Style>
        
       </chartingToolkit:ColumnSeries.DataPointStyle>
    </chartingToolkit:ColumnSeries>
    </chartingToolkit:Chart.Series>
</chartingToolkit:Chart>

This is the view model:

private ObservableCollection<KeyValuePair<DateTime, int>> myGraph;

public ObservableCollection<KeyValuePair<DateTime, int>> MyGraph
{
    get { return myGraph; }
    set 
    {
        myGraph = value;
        OnPropertyChanged();
    }
}
public ChartVM()
{
    MyGraph = new ObservableCollection<KeyValuePair<DateTime, int>>()
    {
        new KeyValuePair<DateTime, int> (DateTime.Now, 8),
        new KeyValuePair<DateTime, int> (DateTime.Now.AddDays(1), 8),
        new KeyValuePair<DateTime, int> (DateTime.Now.AddDays(2), 11),
        new KeyValuePair<DateTime, int> (DateTime.Now.AddDays(3), 7),
        new KeyValuePair<DateTime, int> (DateTime.Now.AddDays(4), 12),
    };
}