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Gets or sets whether the chart group uses a different color or pattern for each data marker.
If this property is true, Microsoft Excel assigns a different color
or pattern to each data marker. The chart must contain only one series.
bool VaryByCategories { get; set; }
Property VaryByCategories As Boolean
IChart chart = worksheet.Shapes.AddChart(ChartType.ColumnClustered, 20, 20, 300, 200).Chart;
IChartGroup chartGroup = chart.ChartGroups[0];
chartGroup.VaryByCategories = true;
bool varyByCategories = chartGroup.VaryByCategories;