I'm looking at example here:
chart_data = ChartData()
chart_data.categories = ['West', 'East', 'North', 'South', 'Other']
chart_data.add_series('Series 1', (0.135, 0.324, 0.180, 0.235, 0.126))
chart = slide.shapes.add_chart(
XL_CHART_TYPE.PIE, x, y, cx, cy, chart_data
chart.has_legend = True
chart.legend.position = XL_LEGEND_POSITION.BOTTOM
chart.legend.include_in_layout = False
chart.plots.has_data_labels = True
data_labels = chart.plots.data_labels
data_labels.number_format = '0%'
data_labels.position = XL_LABEL_POSITION.OUTSIDE_END
Custom coloring on a series is accomplished using the
.fill attribute on the series.
Unfortunately that attribute hasn't been implemented yet for pie charts, only for bar and column charts. http://python-pptx.readthedocs.org/en/latest/api/chart.html#barseries-objects
It is possible to change the default coloring though, in the "template" .pptx file you start with, which accomplishes the same thing for many folks. All the charts in the file will have the same coloring, but it doesn't have to be the built-in defaults.