Hi,
The color of the Column is taken from the BackColor property of the series'' Interior.
series.Style.Interior = new Syncfusion.Drawing.BrushInfo(Syncfusion.Drawing.GradientStyle.None, Color.Black, Color.Orange);
Please see sample linked below:
http://www.syncfusion.com/support/user/Uploads/ChartSeriesColor_5100.zip
Regards,
Davis