void DataPlot_SetColorByCol_ex()
{
	//wks with 3 columns
	int nXCol = 0, nYCol = 1, nCCol = 2;
	Worksheet wks = Project.ActiveLayer();
	DataRange dr;	
	dr.Add(wks, nXCol, "X");
	dr.Add(wks, nYCol, "Y");
	
	//make a line plot
	GraphPage gp;
	gp.Create("Origin");
	GraphLayer gl = gp.Layers();	
	gl.AddPlot(dr, IDM_PLOT_LINE);
        DataPlot dp = gl.DataPlots(0); 
	if( !dp )
		return;
	
	//set line color by theme
	OQCOLOR oqColor;
	okutil_get_ocolor_by_col(&oqColor, nCCol, nYCol, COLTYPE_COLOR_COLORMAP);
	Tree trFormat;
	trFormat.Root.Line.Color.nVal = oqColor;
	int iRet = dp.UpdateThemeIDs(trFormat.Root, "Error", "Unknown tag");
	bool bRet = dp.ApplyFormat(trFormat, true, true);     
	
	gl.Rescale();
}