public class GraduatedColorsRendererDefinition : ClassBreaksRendererDefinition 

{
    var featureLayerCreationParams = new FeatureLayerCreationParams(new Uri(@"c:\data\countydata.gdb\counties"))
    {
        Name = "Population Density (sq mi) Year 2010",
        RendererDefinition = new GraduatedColorsRendererDefinition("POP10_SQMI")
    };
    LayerFactory.Instance.CreateLayer<FeatureLayer>(
      featureLayerCreationParams,
      MapView.Active.Map
    );
}

{
    string colorBrewerSchemesName = "ColorBrewer Schemes (RGB)";
    StyleProjectItem colorBrewerStyle = Project.Current.GetItems<StyleProjectItem>().First(s => s.Name == colorBrewerSchemesName);
    string colorRampName = "Greens (Continuous)";
    //Note: Needs QueuedTask to run
    IList<ColorRampStyleItem> colorRampListFromTheStyle = colorBrewerStyle.SearchColorRamps(colorRampName);

    ColorRampStyleItem colorRampFound = colorRampList[0];
    GraduatedColorsRendererDefinition gcDef = new GraduatedColorsRendererDefinition()
    {
        ClassificationField = "CROP_ACR07",
        ClassificationMethod = ArcGIS.Core.CIM.ClassificationMethod.NaturalBreaks,
        BreakCount = 6,
        ColorRamp = colorRampFound.ColorRamp,
        SymbolTemplate = SymbolFactory.Instance.ConstructPolygonSymbol(
                              ColorFactory.Instance.GreenRGB, SimpleFillStyle.Solid, null).MakeSymbolReference(),
        ExclusionClause = "CROP_ACR07 = -99",
        ExclusionSymbol = SymbolFactory.Instance.ConstructPolygonSymbol(
                              ColorFactory.Instance.RedRGB, SimpleFillStyle.Solid, null).MakeSymbolReference(),
        ExclusionLabel = "No yield",
    };
    var featureLayerCreationParams = new FeatureLayerCreationParams((new Uri(@"c:\Data\CountyData.gdb\Counties")))
    {
        Name = "Crop",
        RendererDefinition = gcDef
    };
    //Note: Needs QueuedTask to run
    LayerFactory.Instance.CreateLayer<FeatureLayer>(featureLayerCreationParams, MapView.Active.Map);
}

/// <summary>
/// Renders a feature layer using graduated colors to draw quantities.
/// ![cb-colors.png](https://ArcGIS.github.io/arcgis-pro-sdk/images/Renderers/cb-colors.png "Graduated colors with natural breaks renderer.")
/// </summary>
{
  //Check feature layer name
  //Code works with the USDemographics feature layer available with the ArcGIS Pro SDK Sample data
  var featureLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault(f => f.Name == "USDemographics");
  if (featureLayer == null)
  {
    MessageBox.Show("This renderer works with the USDemographics feature layer available with the ArcGIS Pro SDK Sample data", "Data missing");
  }

  GraduatedColorsRendererDefinition gcDef = new GraduatedColorsRendererDefinition()
  {
    ClassificationField = "NumericFieldInFeatureLayer",
    ClassificationMethod = ClassificationMethod.NaturalBreaks,
    BreakCount = 5,
    ColorRamp = colorRamp,
  };
  //Note: Run within QueuedTask
  CIMClassBreaksRenderer renderer = (CIMClassBreaksRenderer)featureLayer.CreateRenderer(gcDef);
  featureLayer?.SetRenderer(renderer);
}

/// <summary>
/// Renders a feature layer using graduated colors to draw quantities. The outline width is varied based on attributes.
/// ![graduatedColorOutline.png](https://ArcGIS.github.io/arcgis-pro-sdk/images/Renderers/graduatedColorOutline.png "Graduated colors with natural breaks renderer.") 
/// </summary>
{
  //Check feature layer name
  //Code works with the USDemographics feature layer available with the ArcGIS Pro SDK Sample data
  var featureLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault(f => f.Name == "USDemographics");
  if (featureLayer == null)
  {
    MessageBox.Show("This renderer works with the USDemographics feature layer available with the ArcGIS Pro SDK Sample data", "Data missing");
  }
  //Gets the first numeric field of the feature layer
  var firstNumericFieldOfFeatureLayer = "NumericFieldInFeatureLayer";
  //Gets the min and max value of the field
  var minMax = GetFieldMinMax(featureLayer, firstNumericFieldOfFeatureLayer);
  GraduatedColorsRendererDefinition gcDef = new GraduatedColorsRendererDefinition()
  {
    ClassificationField = "NumericFieldInFeatureLayer",
    ClassificationMethod = ClassificationMethod.NaturalBreaks,
    BreakCount = 5,
    ColorRamp = colorRamp
  };
  CIMClassBreaksRenderer renderer = (CIMClassBreaksRenderer)featureLayer.CreateRenderer(gcDef);
  //Create array of CIMVisualVariables to hold the outline information.
  var visualVariables = new CIMVisualVariable[] {
              new CIMSizeVisualVariable
              {
                  ValueExpressionInfo = new CIMExpressionInfo
                  {
                     Title = "Custom",
                     Expression = "$feature.AREA",
                     ReturnType = ExpressionReturnType.Default
                  },
                  AuthoringInfo = new CIMVisualVariableAuthoringInfo
                  {
                      MinSliderValue = Convert.ToDouble(minMax.Item1),
                      MaxSliderValue = Convert.ToDouble(minMax.Item2),
                      ShowLegend = false,
                      Heading = firstNumericFieldOfFeatureLayer
                  },
                  VariableType = SizeVisualVariableType.Graduated,
                  Target = "outline",
                  MinSize = 1,
                  MaxSize = 13,
                  MinValue = Convert.ToDouble(minMax.Item1),
                  MaxValue = Convert.ToDouble(minMax.Item2)
              },

          };
  renderer.VisualVariables = visualVariables;
  //Note: Run within QueuedTask
  featureLayer?.SetRenderer(renderer);
}