You can use this to change the pie (slices color). Change the default-color0 up to the number of slices you have
Dim style0 As Map = PieChart.GetChildStyleMap(".default-color0.chart-pie")
style0.put("-fx-background-color", "#FF0000")
PieChart.SetChildStyleMap(".default-color0.chart-pie",style0)
For the legend, I will have to check the documentation