Hi
Here it is a update to my old samples that I've put here some time ago.

Even after evaporating (and concentrating) the Waterman blue-black, the ink has still a turquoise sign, but not green, now.
Caran d'Ache Blue Night is a nice dark blue, almost black/gray. (It is not a true blue-black ink)
Waterman Florida Blue and Caran d'Ache Blue Sky are similar, but the last is a bit pale and somewhat purple, like royal blue.
Montblac Blue-Black, is for me the only true among these BB's. It contains some gall iron compounds (bad for the pens).
Carabbean Sea has an interesting color, in the domain of the turquoise colors, but not accuratly turquoise.
Havana is also a nice brown.