A few years ago, Jonas Whale showed me how to set a custom icon for a folder, in this thread:
I’ve been trying to figure out how to set a custom icon for an alias of a folder, and can’t manage it. Any operation I perform on the alias gets performed on the original folder, not the alias.
What this is about: the standard macOS folder icons seem blindingly bright to me, and I replace the folder aliases on my desktop with a darker version of the standard icon. I do this by hand: Cmd-I on the alias, paste the icns file. This takes time, and macOS sometimes reverts to the standard icon. If there’s a way to write an AppleScript that will change the icon when I drop an alias on the the AppleScript app, I’ll be very grateful to learn about it.