You can vary the colors of data markers within the same data series in doughnut charts and in single-series charts. The colors of slices in pie charts and doughnut charts are varied by default.
Click the data series that you want to change the colors for.
On the Format menu, click Selected Data Series or Selected Data Point, and then click the Options tab.
Select the Vary colors by point check box or the Vary colors by slice check box.