The lyrics are hard-hitting, but not easy to understand literally. Could the song be addressed to Joan Baez, as some believe? Or was he saying goodbye to a part of himself?
Who knows? Maybe the question of who Baby Blue was isn't even the right question. In any case, the song was sung by Joan Baez and many other greats, including The Animals, Bonnie Raitt, Judy Collins and Marianne Faithfull.
That's as well as the great bard and composer Bob Dylan himself.