After replacing the files: SidebarGenericFolder.icns , GenericFolderIcon.icns and GenericOpenFolderIcon.icns with different colored files in /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources (SIP disabled and as a root user)
I've had all of my blue folders change to blank documents as their icon. What can I do to reverse this or make them appear as the .icns icon I attempted to replace them with?
MacBook Air
If you've been making regular backups with time machine Use Time Machine to restore deleted files or older files - Apple Support
Depending on the changes made to your system, it might be worth the peace of mind to simply restore everything. Restore your Mac from a backup - Apple Support
In general, it's best to avoid disabling SIP unless you really know what you're doing. I've never had any reason to modify anything in the /System folder. In the future, I'd consider it off limits.
Folder Icons appearing as blank documents
