Hello, Asghar,
Note that most of the forum threads are reviewed by Telerik representatives and sometimes we address the questions asked by our customers in the forums as well. However, a post in the forum doesn't guarantee you a response from the Telerik support team. Moreover, threads are handled according to license and time of posting, so if it is an urgent problem, we suggest you use a support ticket, which would be handled before a forum thread. Thank you for your understanding.
In order to specify the border color, it is necessary to set the AreaSeries.
BorderColor property:
AreaSeries areaSeries = new AreaSeries();
areaSeries.BackColor = Color.Yellow;
areaSeries.BorderColor = Color.Red;
areaSeries.DataPoints.Add(new CategoricalDataPoint(13, "Jan"));
areaSeries.DataPoints.Add(new CategoricalDataPoint(20, "Apr"));
areaSeries.DataPoints.Add(new CategoricalDataPoint(15, "Jul"));
areaSeries.DataPoints.Add(new CategoricalDataPoint(16, "Oct"));
this.radChartView1.Series.Add(areaSeries);

I hope this information helps.
Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik
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