Hi Omer,
You can set series appearance declaratively in XAML like this:
<telerikChart:RadChart VerticalAlignment="Top">
<telerikChart:RadChart.DefaultView>
<telerikCharting:ChartDefaultView>
<telerikCharting:ChartDefaultView.ChartTitle>
<telerikCharting:ChartTitle Content="Year 2009" HorizontalAlignment="Center"/>
</telerikCharting:ChartDefaultView.ChartTitle>
<telerikCharting:ChartDefaultView.ChartLegend>
<telerikCharting:ChartLegend x:Name="chartLegend" UseAutoGeneratedItems="True" />
</telerikCharting:ChartDefaultView.ChartLegend>
<telerikCharting:ChartDefaultView.ChartArea>
<telerikCharting:ChartArea LegendName="chartLegend">
<telerikCharting:ChartArea.DataSeries>
<!-- Bar Chart -->
<telerikCharting:DataSeries LegendLabel="Expenses">
<telerikCharting:DataSeries.Definition>
<telerikCharting:BarSeriesDefinition>
<telerikCharting:BarSeriesDefinition.Appearance>
<telerikCharting:SeriesAppearanceSettings Fill="DodgerBlue"/>
</telerikCharting:BarSeriesDefinition.Appearance>
</telerikCharting:BarSeriesDefinition>
</telerikCharting:DataSeries.Definition>
<telerikCharting:DataPoint YValue="45" XCategory="Jan"/>
<telerikCharting:DataPoint YValue="48" XCategory="Feb"/>
<telerikCharting:DataPoint YValue="53" XCategory="Mar"/>
<telerikCharting:DataPoint YValue="41" XCategory="Apr"/>
<telerikCharting:DataPoint YValue="32" XCategory="May"/>
<telerikCharting:DataPoint YValue="28" XCategory="Jun"/>
<telerikCharting:DataPoint YValue="63" XCategory="Jul"/>
<telerikCharting:DataPoint YValue="74" XCategory="Aug"/>
<telerikCharting:DataPoint YValue="77" XCategory="Sep"/>
<telerikCharting:DataPoint YValue="85" XCategory="Oct"/>
<telerikCharting:DataPoint YValue="89" XCategory="Nov"/>
<telerikCharting:DataPoint YValue="80" XCategory="Dec"/>
</telerikCharting:DataSeries>
</telerikCharting:ChartArea.DataSeries>
</telerikCharting:ChartArea>
</telerikCharting:ChartDefaultView.ChartArea>
</telerikCharting:ChartDefaultView>
</telerikChart:RadChart.DefaultView>
</telerikChart:RadChart>
Hope it will help you
Regards
Rahul