Blue Folders
If so, this simply means you are working offline and not connected live to the vault server. This happens when you click the Work Offline button on the vault login screen, or attempt to login when you are disconnected from your network, it will default to offline since you are after all, offline.
Return to Green Folders
The solution is an easy one — within Windows Explorer > click on your vault view folder > in the Tools menu > select Work On-line.
Work On-line
Your vault view will now connect to the actual vault and your folders will go back to being green.
Green Folders