The Graph item comes with built-in palettes, and you can define additional custom palette. These palette colors also appear in the legend. When multiple series are added to the chart, the chart assigns the series a color in the order that the colors have been defined in the palette.
For example check out the Dashboard demo report that illustrates Graphs with multiple series.
However if your goal is to have different colors to the same series items, our suggestion is to set up a Stacked Column chart type with Categories and Series set to the same field.
the Telerik team
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