I can only advise anyone to try Diamine Prussian Blue - lovely stuff if you like anything that is at all blue. One of my favourites.
The Imperial Purple is great too. One of my favourites.
So is the Registrars Ink (though I am advised to flush the pen reasonably often and not to leave it sitting unused for months) - the way ti changes colour is
I will try other Diamine inks but keep changing my mind about which. Ah for the time and money to try them all
I was disappointed with the (original, plain) Black as it was not super-dark, so I tend to play with it mixing it with other stuff. But, it does give nice shading and it flows well and has all the other Diamine positives.
If you want a black that is less :ph34r: than the Aurora and Pelikan and others, it might appeal to you.
Perhaps I should try their new black, or their other new colours....
Chris