How can I fix grey folders on my MacBook?

I would try changing the color, then change it back to automatic.

I don’t have any ideas on why they are gray. Since everything works normally, the folder color was my best guess.

When there is a problem, the folders are subdued, not just gray, and they don’t work. Then there is the “gray” color when viewing hidden files in Finder. None of that seems to match what you described.

tastaur wrote:

All my folders on my MacBook 14" are suddenly grey (but not on my iPad or my phone) - every single folder at every level, including Documents, Desktop, etc. I can still access the folders and the folder content, and I can seemingly create new content and delete old content - in other words, everything seems to work.

If something is not broken I would not endeavor to fix it. Others provided suggestions about folder color if that is really bothering you.

When I connect my Time Machine it starts counting tens, if not hundreds, of thousands of changed files (it seems like it is in the process of registering that every single folder and file has changed - which, in a sense, they have), at which point I skip the back-up...

So this is a separate issue that has nothing to do with grey folders on your Mac.

Every time you skip the backup, that will increase the time for the next backup in counting up files and preparing for the backup.

When my Mac executes Time Machine backups, it often finds many thousands of "changed" files. But the incremental backups take only ~ seconds. The longer you go between TM backups, the longer the next one takes.

The closest explanation I have seen is that ejecting an external hard drive too quickly may cause this problem (and I may inadvertently have done exactly that, not sure) - but that should still resolve itself with a simple reboot, shouldn't it?

You are not sure? That indeed may explain why your next backup is taking a longer time than expected. If there is directory damage on the external drive, a simple reboot won't fix that. If you believe the drive is damaged, you should run Disk Utility First Aid on that external drive.

There is a System Setting to set the folder color. I think it is in Appearance.