Thanks for the question.
Why don't you simply clone the existing palette and tweak it? It's easier. Take a look at the example below:
RadCartesianChartView chartView = new RadCartesianChartView(this);
ChartPalette customPalette = chartView.getPalette().clone();
PaletteEntry entry = customPalette.getEntry(ChartPalette.LINE_FAMILY, 0);
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