public class CIMVoxelUniqueValueRenderer : CIMVoxelRenderer, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

{
  var variable = voxelLayer.GetVariableProfiles().First();
  var renderer = variable.Renderer;
  if (variable.DataType == VoxelVariableDataType.Continuous)
  {
    //Renderer will be stretch
    var stretchRenderer = renderer as CIMVoxelStretchRenderer;
    //access the renderer

  }
  else //VoxelVariableDataType.Discrete
  {
    //Renderer will be unique value
    var uvr = renderer as CIMVoxelUniqueValueRenderer;
    //access the renderer
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    //Get the variable profile whose renderer will be changed
    var variable = voxelLayer.SelectedVariableProfile;

    //Check DataType
    if (variable.DataType != VoxelVariableDataType.Discrete)
      return;//must be Discrete to have a UV Renderer...

    var renderer = variable.Renderer as CIMVoxelUniqueValueRenderer;

    //A CIMVoxelUniqueValueRenderer consists of a collection of
    //CIMVoxelColorUniqueValue classes - one per discrete value
    //in the associated variable profile value array

    //Get the first class
    var classes = renderer.Classes.ToList();
    var unique_value_class = classes.First();
    //Set its visibility off
    unique_value_class.Visible = false;

    //Apply the change to the renderer
    renderer.Classes = classes.ToArray();
    //apply the changes
    variable.SetRenderer(renderer);
  }
}