How can I add OS X “tags” to files programmatically?

Question

Since Mavericks, OS X has had the ability to tag & colour files in Finder.

Is there any

Answer 1

The OpenMeta framework is a third-party standard for adding metadata to OS X files using extended attributes. It is used by a number of third-party applications.

Or you can use the XATTR command to manipulate the extended attributes via command line.