How can you restore normal icons?

I had this problem as well. I don't know a way to globally fix it.

It is a royal pain to fix all of them, but you can restore the folder icon for each individual folder easily:

1) select a folder with a "good" icon

2) "get info" (Command-I) on the folder

3) click on the folder icon in the upper left corner and copy it (Command-C)

4) Select a folder with a "bad" icon and "get info"

5) click on the folder icon in the upper left corner and paste in the proper icon (Command-P)

This will restore the icon for that folder. You an also use this to paste any image you want to use for the folder.

I had this issue also. Tech support assistance came up with this solution. Would not recommend applying to applications.

In a terminal window issue the command below.

xattr -d -r com.apple.FinderInfo <folder name>

(can add -r if you trust applying recursively)

  Try a SafeBoot https://support.apple.com/en-us/HT201262

  Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache,  etc.  You can login and test. Reboot as normal and test.

In some instances clearing caches may be enough to restore your system icons.

Same with me. I updated a clone of my startup drive that is on an external ssd first. About a third of the folders in the documents folder had a generic file icon instead of the normal folder icon. They seemed to be older folders. When I booted from the external drive, the same folders on the internal drive also showed the file icon. I decided to go ahead and update the internal drive to Catalina and those folders again had the file icon. I ended up creating new folders with the same names, moving the contents and replacing the now empty folders. It took a while, and I probably missed some deeply buried folders, but it made me crazy.

This fix can be applied to numerous folders at once. Simply select all the folders you want to change, click Command-I, and change the folder icon in the top left as you described above. The change will apply to all the selected folders.

WARNING: OK so I did this and it fixed the problem. It complained about a few files not having Permission which I ignored. On finishing though when delving through my folders I noticed a few aliases to folders in shared Dropbox folders were no longer aliases. Ouch. I tested this on a single folder with an alias in it and it turned the alias into an ordinary file. Luckily I have only a dozen or so of these which need fixing. Just have to remember where they pointed to !

Did you try rebooting.

The copy and paste works well, except for folders that you have in the Finder's Sidebar. It still shows the file icon.

This is the true global solution.