© 2010 Autodesk
Introduction to the Navisworks 2011 .NET API
Modifying The Model
Change Current Selection
IEnumerable<ModelItem> items =
  Application.ActiveDocument.Models.GetRootItems().DescendantsAndSelf.
    Where(x => x.IsHidden = false);
Application.ActiveDocument.CurrentSelection.CopyFrom(items);
Override Colour
Application.ActiveDocument.Models.OverridePermanentColor(items, Color.Red);
Change Tool
Application.ActiveDocument.Tool = Tool.Select;
Firstly, we can modify the current selection. Here, we are using LINQ to select all visible items, and then selecting them.
Next, we are using the DocumentModels part to override the colour to red.
And finally we are changing the active tool to the Select tool.