I have no spoilers, but we all (4 of us watching) thought Danny Pink was Journey Blue's brother - the one dead or maybe mostly-dead in the spaceship with her at the beginning - somehow removed in time and space. Whether the Doctor somehow saved him, or Missy did, or what - I don't know - but it seems too coincidental to introduce a random handsome black man with a colour name who used to be a soldier, and then also have a handsome black woman with a colour name who is also a soldier!