About arrow hierarchy in Lookup windows
Some Lookup windows have a left and right pane. The left pane displays the classes, and the right pane displays the contents of the class that you select. You can click the triangle next to a class to open or close it. The color of the triangle indicates whether you can display more subclasses.
| 
                                                                     Color  | 
                                                                
                                                                     Description  | 
                                                            
|---|---|
| 
                                                                     Red  | 
                                                                
                                                                     The class cannot be expanded any further (end of the branch).  | 
                                                            
| 
                                                                     Blue  | 
                                                                
                                                                     Currently selected class showing all subclasses.  | 
                                                            
| 
                                                                     Green  | 
                                                                
                                                                     Contains subclasses and can be opened by clicking the plus sign (always displays a plus sign).  |