Like most pen-makers, Platinum has also taken to ink production. They are, in fact, extremely diverse in their ink production, as in addition to the usual dye-based fountain pen inks, they have “ultrafine particle pigment inks” and “carbon ink”, both of which call for attention to pen hygiene in a higher degree than usual, and the latter of which they actually make special pens to handle (not unlike Parker’s old arrangement for the “51”). They also produce non-aqueous dye-based inks for markers and highlighters, and the problematic aspect of this bounty of different inks is that they all come in the same shape of cartridge. Fountain pen users will want to watch product codes: SPN and SPSQ is on the safe cartridges, INK on the bottles (as opposed to INKG or INKC).
Examples (note– I’ve not calibrated my scanner, so these are mere approximations of the true colour):
Black: It’s black. Like most fountain pen-safe blacks, it’s not utterly lightless– for that you’re going to want their carbon black.
Blue-black: Rather more in the blue family than a lot of blue-blacks; it’s like a slightly darker version of Herbin’s Bleu Nuit.