jQuery PolarChart - series.point.selectionStyle.border
To set custom border settings specific to the 'selected' state for points in all series at once, use the properties of the commonSeriesSettings.point.selectionStyle.border configuration object.
To set custom border settings specific to the 'selected' state for points in all series of a single type at once, use the properties of the corresponding object within commonSeriesSettings (e.g. area.selectionStyle.border). The values that are set within this object override the corresponding common values that are set within the root commonSeriesSettings.selectionStyle.border object.
In case you have to set a selection style property for a point border in an individual series, use the selectionStyle.border object within the series object of the series array. The values that are set individually override corresponding common values.