public double MaximumValue {get;}

{
  //Get the variable profile on which to access the data
  var variable = voxelLayer.SelectedVariableProfile;
  //or use ...voxelLayer.GetVariableProfiles()

  //Data range
  var min = variable.Statistics.MinimumValue;
  var max = variable.Statistics.MaximumValue;

  //Color range (Continuous only)
  double color_min, color_max;
  if (variable.DataType == VoxelVariableDataType.Continuous)
  {
    var renderer = variable.Renderer as CIMVoxelStretchRenderer;
    color_min = renderer.ColorRangeMin;
    color_max = renderer.ColorRangeMax;
  }
}

{
  //Typically, the default color range covers the most
  //commonly occurring voxel values. Usually, the data
  //range is much broader than the color range

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

    //Check DataType
    if (variable.DataType != VoxelVariableDataType.Continuous)
    {
      //must be continuous to have a Stretch Renderer...
    }

    var renderer = variable.Renderer as CIMVoxelStretchRenderer;
    var color_min = renderer.ColorRangeMin;
    var color_max = renderer.ColorRangeMax;
    //increase range by 10% of the current difference
    var dif = (color_max - color_min) * 0.05;
    color_min -= dif;
    color_max += dif;

    //make sure we do not exceed data range

    if (color_min < variable.Statistics.MinimumValue)
      color_min = variable.Statistics.MinimumValue;
    if (color_max > variable.Statistics.MaximumValue)
      color_max = variable.Statistics.MaximumValue;

    //variable.Statistics.MinimumValue
    renderer.ColorRangeMin = color_min;
    renderer.ColorRangeMax = color_max;

    //apply changes
    variable.SetRenderer(renderer);
  }
}