how do a share a generator

My partner and I are passing a hard drive back and forth between the two of us while collaborating on a documentary. All assets are contained in the FCPX Library on the drive and everything is translating between the two of us without issue. EXCEPT for generators that I created from scratch in Motion and published to FCPX. They work fine on my computer but show up in red when passed to my partner. He can open on his computer the Motion files I created on my computer, and he can then publish them to FCPX on his computer and use them on the time line. However, when he passes the drive back to me, whatever he worked on shows up in red.

Because Generators (and Titles, Transitions, and Effects) that are native to FCPX can be smoothly used and passed back and forth between the two of us, I am assuming that our problem is that the Generators I have created in Motion are not really on the external hard drive we are passing back and forth. How do we successfully use these unique Generators within our collaboration? If that is not possible, then it means we have to limit ALL work involving these Generators to a single computer which really destroys our workflow.

Thank you in advance for any and all help!