How do I restore the default folder icon?
Get Info on the folder.
Click the icon on the top-left of the window.
Press ⌘X or Backspace


Alternatively, cd into the directory and run

rm Icon$'\r'




To delete the icon from multiple folders at the same time, run the following command:

find ~/Desktop -name Icon$'\r' -delete


Replace ~/Desktop with the containing folder of the folders that you wish to remove the icons from.