Selection color is different for just one of my folders?


For my project (a novel) I have organized it so each chapter is a folder in the left-hand sidebar. Just moments ago I went to select all the folders for a given character and change the icons, when I noticed that, weirdly, exactly one of my folders (out of nearly 100) has a different highlight color (grey instead of dark purple):
[attachment=0]Scrivener issue.png[/attachment]
You can see the folders above and below are the normal white color, not selected, while the selected folders are highlighted purple, except for “Desh 4”? What does this mean? I clicked around my project, compared this folder to the other “normal” (purple highlight) folders, and see no differences. I don’t think I did anything special to this folder when creating or manipulating it either. And I could not find any other help topics on this. So I’m totally baffled! Any insight would be appreciated!