AnalysisDisplayStyle

Document doc = commandData.Application.ActiveUIDocument.Document;

AnalysisDisplayStyle analysisDisplayStyle = null;
// Look for an existing analysis display style with a specific name
FilteredElementCollector collector1 = new FilteredElementCollector(doc);
ICollection<Element> collection = collector1.OfClass(typeof(AnalysisDisplayStyle)).ToElements();
var displayStyle = from element in collection 
                   where element.Name == "Display Style 1" 
                   select element;

// If display style does not already exist in the document, create it
if (displayStyle.Count() == 0)
{
    AnalysisDisplayColoredSurfaceSettings coloredSurfaceSettings = 
        new AnalysisDisplayColoredSurfaceSettings();
    coloredSurfaceSettings.ShowGridLines = true;

    AnalysisDisplayColorSettings colorSettings = new AnalysisDisplayColorSettings();
    Color orange = new Color(255, 205, 0);
    Color purple = new Color(200, 0, 200);
    colorSettings.MaxColor = orange;
    colorSettings.MinColor = purple;

    AnalysisDisplayLegendSettings legendSettings = new AnalysisDisplayLegendSettings();
    legendSettings.NumberOfSteps = 10;
    legendSettings.Rounding = 0.05;
    legendSettings.ShowDataDescription = false;
    legendSettings.ShowLegend = true;

    analysisDisplayStyle = AnalysisDisplayStyle.CreateAnalysisDisplayStyle(doc, 
        "Display Style 1", coloredSurfaceSettings, colorSettings, legendSettings);
}
else
{
    analysisDisplayStyle = displayStyle.Cast<AnalysisDisplayStyle>().ElementAt<AnalysisDisplayStyle>(0);
}

// now assign the display style to the view
doc.ActiveView.AnalysisDisplayStyleId = analysisDisplayStyle.Id;