public class ColorFactory : IColorFactory  

//Must be on QueuedTask.Run(() => { ...

//Build geometry
Coordinate2D center = new Coordinate2D(2, 2.75);
var eabElp = new EllipticArcBuilderEx(center, 0, 1, 0.45, 
                                       ArcOrientation.ArcClockwise);
var ellipse = eabElp.ToSegment();

//Set symbolology, create and add element to layout
CIMStroke outline = SymbolFactory.Instance.ConstructStroke(
                                ColorFactory.Instance.GreenRGB, 2.0,
                        SimpleLineStyle.Dot);
CIMPolygonSymbol ellipseSym = SymbolFactory.Instance.ConstructPolygonSymbol(
                         ColorFactory.Instance.GreyRGB, SimpleFillStyle.Vertical, 
                                                  outline);

var poly = PolygonBuilderEx.CreatePolygon(
  PolylineBuilderEx.CreatePolyline(ellipse, AttributeFlags.AllAttributes));

var elpElm = ElementFactory.Instance.CreateGraphicElement(
  container, poly, ellipseSym, "New Ellipse");

/// <summary>
/// Create a mesh symbol that can be applied to a multi-patch feature layer.
/// </summary>
/// <remarks>
/// A mesh symbol is a CIMMeshSymbol object.  Define an array of CIMSymbolLayers which contains a CIMMaterialSymbol layer with the specified properties such as Color, etc.
/// Assign this array of CIMSymbolLayers to the CIMMeshSymbol.
/// ![MeshSymbolOrange](http://Esri.github.io/arcgis-pro-sdk/images/Symbology/mesh-material-orange.png)
/// </remarks>
/// <returns></returns>
public static Task<CIMMeshSymbol> CreateMeshSymbolAsync()
{
    return QueuedTask.Run<CIMMeshSymbol>(() =>
   {
       CIMSymbolLayer[] materialSymbolLayer =
      {
            new CIMMaterialSymbolLayer()
            {
                Color = ColorFactory.Instance.CreateRGBColor(230,152,0),
                MaterialMode = MaterialMode.Multiply
            }
       };
       var myMeshSymbol = new CIMMeshSymbol()
       {
           SymbolLayers = materialSymbolLayer
       };
       return myMeshSymbol;
   });
}