Long time no ink review (well, the sun hasn't been out that often this year). Diamine Prussian Blue is a medium slate blue with a mildly watery consistency. I picked the color because it looks just like the color of the German music publisher G. Henle Verlag (One would always gets some glance of approval from professors/TAs if you carry the blue book around the practice room ). Even without the connection with that prestigious publisher, it still seems like an interesting subdued shade for everyday uses.
Prussian blue - as with may gray-toned color, is watery, smooth on the paper (Daolin/writes-like-Rhodia refills that fits the bigger Midori traveller's, which btw mine is not...) and shades very well with a Lamy medium steel nib. There is very minimal feathering (on the start of writing which tend to be wetter) and no bleed-through but I guess it would be different on more porous paper. The dry time was ok, maybe within 15 second and the ink withstand like spill of water, just not smear/soak.
Writing sample was Edith Piaf's Under the Parisian Sky (if you Google Parisian sky, most pictures are in this kind of slate blue...and that MAC eyeshadow of the same shade).