psdncjet black, the other three are dark blues. see the ink images from JetPens accessed via this page: https://www.jetpens.com/Diamine-Jet-Black-Ink-30-ml-Bottle/pd/13587 (personally, I really like trying out Goulet's 2 mL ink samples before buying bottles, but I'm in the US so buying inks from JetPens or Goulet might not make sense for you.)
(personally, I really like trying out Goulet's 2 mL ink samples before buying bottles, but I'm in the US so buying inks from JetPens or Goulet might not make sense for you.)