On July 11, he RFK, Jr./Shanahan Campaign handed in its petition signatures to the Colorado Secretary of State.
UPDATE: see this story.
Presuming that the Campaign has enough valid signatures (I don’t know how many signatures were turned in, but I would be shocked if they didn’t have enough valid signatures of Colorado registered voters), this would mean that Kennedy/Shanahan would be on the ballot as an Independent ticket, and not on the Libertarian Party line in that state, because Colorado does not allow candidate fusion.