public static StyleItem LookupItem( 
   StyleProjectItem styleProjectItem,
   StyleItemType type,
   string key
)

{
    //Search for a specific point symbol in style
    //Note: styleProjectItem was created above in the variable initialization section
    //Note: Needs QueuedTask to run
    string key = "Circle 1_Shapes_3";
    SymbolStyleItem item = (SymbolStyleItem)styleProjectItem.LookupItem(StyleItemType.PointSymbol, key);
}

{
  // Note: call within QueuedTask.Run()
  {
    var fields = pointCloudSceneLayer.GetAvailablePointCloudRendererFields(
                       PointCloudRendererType.ClassBreaksRenderer);
    var classBreakDef = new PointCloudRendererDefinition(
                              PointCloudRendererType.ClassBreaksRenderer)
    {
      //ELEVATION or INTENSITY
      Field = fields[0]
    };
    //create the renderer
    var cbr = pointCloudSceneLayer.CreateRenderer(classBreakDef)
                              as CIMPointCloudClassBreaksRenderer;
    //Set up a color scheme to use
    var style = Project.Current.GetItems<StyleProjectItem>()
                               .First(s => s.Name == "ArcGIS Colors");
    var rampStyle = style.LookupItem(
      StyleItemType.ColorRamp, "Spectrum By Wavelength-Full Bright_Multi-hue_2")
                                                                as ColorRampStyleItem;
    var colorScheme = rampStyle.ColorRamp;
    //Set up 6 manual class breaks
    var breaks = 6;
    var colors = ColorFactory.Instance.GenerateColorsFromColorRamp(
                                                colorScheme, breaks);
    var classBreaks = new List<CIMColorClassBreak>();
    var min = cbr.Breaks[0].UpperBound;
    var max = cbr.Breaks[cbr.Breaks.Count() - 1].UpperBound;
    var step = (max - min) / (double)breaks;

    //add in the class breaks
    double upper = min;
    for (int b = 1; b <= breaks; b++)
    {
      double lower = upper;
      upper = b == breaks ? max : min + (b * step);
      var cb = new CIMColorClassBreak()
      {
        UpperBound = upper,
        Label = string.Format("{0:#0.0#} - {1:#0.0#}", lower, upper),
        Color = colors[b - 1]
      };
      classBreaks.Add(cb);
    }
    cbr.Breaks = classBreaks.ToArray();
    pointCloudSceneLayer.SetRenderer(cbr);
  }
}