I have long been baffled by a particular external hard drive of mine which consist a few random files which are greyed out. I cannot see any abnormality via File Info in Mac or Windows, and most Google search returned solutions that don’t work at all. Worst of all, if I try to “hack” it by moving the file to another location, I end up losing the file entirely!
Finally, a little digging in “Terminal” using ls -la command, I discovered those greyed out files having an attribute of -rwxrwxrwx@, ah ha, the “@” might be all the culprit. Eventually I found out that stands for extended properties. And to view the extended properties, I just need to use xattr -l filename command. In my case, the greyed out files all have this weird com.apple.FinderInfo attribute. To remove that attribute, I run xattr -d com.apple.FinderInfo filename, and the file is back to normal!