public string Field {get; set;}

//Must be called on the MCT
//var pcsl = ...;

//At 2.x - var fields = pcsl.QueryAvailablePointCloudRendererFields(
//                          PointCloudRendererType.ClassBreaksRenderer);

var fields = pcsl.GetAvailablePointCloudRendererFields(
                     PointCloudRendererType.ClassBreaksRenderer);
var classBreakDef = new PointCloudRendererDefinition(
                          PointCloudRendererType.ClassBreaksRenderer)
{
  //ELEVATION or INTENSITY
  Field = fields[0]
};
//create the renderer
var cbr = pcsl.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();
pcsl.SetRenderer(cbr);