Example:

Document doc = new Document();
DocumentBuilder builder = new DocumentBuilder();

Shape shape = builder.insertChart(ChartType.COLUMN, 432.0, 252.0);
Chart chart = shape.getChart();
ChartSeries series = chart.getSeries().get(0);

double minValue = Double.MAX_VALUE;
int minValueIndex = 0;
double maxValue = -Double.MAX_VALUE;
int maxValueIndex = 0;

for (int i = 0; i < series.getYValues().getCount(); i++)
{
    // Clear individual format of all data points.
    // Data points and data values are one-to-one in column charts.
    series.getDataPoints().get(i).clearFormat();

    // Get Y value.
    double yValue = series.getYValues().get(i).getDoubleValue();

    if (yValue < minValue)
    {
        minValue = yValue;
        minValueIndex = i;
    }

    if (yValue > maxValue)
    {
        maxValue = yValue;
        maxValueIndex = i;
    }
}

// Change colors of the max and min values.
series.getDataPoints().get(minValueIndex).getFormat().getFill().setForeColor(Color.RED);
series.getDataPoints().get(maxValueIndex).getFormat().getFill().setForeColor(Color.GREEN);

doc.save(getArtifactsDir() + "Charts.GetChartSeriesData.docx");