I believe you get this in UWP/universal chart, as the others do not feature such appearance. In order to get rid of the semi-transparent mask you will need to implement custom renderer. The process is described for iOS here
. It would be similar for UWP. Once you have obtained reference to the native control, you will have to update the PieSeries.HighlightBrush property. Here is a sample implementation:
MyPieRenderer : PieChartRenderer
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