i use blue inks a lot, specially for signing docs. here is a scan of most of the inks i use. i've included some others, like shoreline gold by PR and cocoa by Swisher (made by Noodlers). there still a two others i didn't include cos' i got no pen inked with those. they are emerald and midnight black, both by Swisher.
my most used are the Private Reserve midnight blues, which IMHO, is a true blue-black; and dc supershow blue which lubricates very well. i just bought Naples Blue and it has great shading. i also got a bottle of Diamine Blue black, but i don't have any comments on this one cos' i haven't used it too much yet... pretty color though!!
I'm more of a green & purple kid, but blues make it into the rotation from time to time.
I really like that Naples blue. I've not tried it yet, but it's now on the list. 80% of my inks are either PR or Noodlers. The rest are either diamine or vintage sheaffer skrip. I love the persian rose & peacock blue I found last month. My all time non green (my signature color) is Diamine Imperial Purple. The richest most intense purple I've found.
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Tu ne cede malis sed contra audentior ito ~Yield not to misfortunes, but advance all the more boldly against them
diamine BB: love the color!!! but is a bit dry, doesn't flow very well. it performed terribly in my aero p51.
i use it in some of my wet writers!!
another thing to watch out for is that it condenses on the nib always leaving a wet powdery residue on the nib and section and have to wipe and clean often.