Use Javascript ChartModify event and here is the sample code:
var palette = anychart.palettes.distinctColors();
palette.items(["#64B5F6", "#2374B8", "#97BDC1", "#FFD54F", "#EF6C00", "#0AB4DE", "#CFAE83"]);
chart.palette(palette);
If your pie chart has more slices than number of colors you specified, colors will be repeated.