Oh, I would have accepted the leprosy alone; but not leprosy and eroticism together, oh no, for the love of God, erotic leprosy?
Blue = Hapag and Lloyd ships
Black = mainly Cunard
White = mainly White Star
red/green = mixes of other lines
This is where it comes from. For reasons of playability, there had to be a few adjustments, in order to ensure that each decade comes with exactly two steamships per different flag.
From this thread: https://boardgamegeek.com/article/27246602#27246602