public CIMPointSymbol ConstructPointSymbol( 
   CIMColor color,
   double size,
   SimpleMarkerStyle style
)

{
    CIMPointSymbol starPointSymbol = SymbolFactory.Instance.ConstructPointSymbol(ColorFactory.Instance.RedRGB, 10.0, SimpleMarkerStyle.Star);
}

/// <summary>
/// Creates a point symbol with custom fill and outline          
/// ![PointSymbolMarker](https://ArcGIS.github.io/arcgis-pro-sdk/images/Symbology/point-fill-outline.png)
/// </summary>
{
  //Note: Run withing QueuedTask
  var circlePtCustomFileOutlineSymbol = SymbolFactory.Instance.ConstructPointSymbol(ColorFactory.Instance.BlueRGB, 6, SimpleMarkerStyle.Circle);
  //Modifying this point symbol with the attributes we want.
  //getting the marker that is used to render the symbol
  var marker = circlePtCustomFileOutlineSymbol.SymbolLayers[0] as CIMVectorMarker;
  //Getting the polygon symbol layers components in the marker
  var polySymbol = marker.MarkerGraphics[0].Symbol as CIMPolygonSymbol;
  //modifying the polygon's outline and width per requirements
  polySymbol.SymbolLayers[0] = SymbolFactory.Instance.ConstructStroke(ColorFactory.Instance.BlackRGB, 2, SimpleLineStyle.Solid); //This is the outline
  polySymbol.SymbolLayers[1] = SymbolFactory.Instance.ConstructSolidFill(ColorFactory.Instance.GreenRGB); //This is the fill
  //To apply the symbol to a point feature layer
  //var renderer = pointLayer.GetRenderer() as CIMSimpleRenderer;
  //renderer.Symbol = circlePtCustomFileOutlineSymbol.MakeSymbolReference();
  //pointLayer.SetRenderer(renderer);
}