Dueing this wonderful period with no pubs/bars/restaurants and the like open, I thought I'd just scan some of my currently-inked Blue-Black inks. I do have others around but these were the first pens that came to hand. I wasn't totally surprised at the results but in one case, quite a bit. As usual, they were done on some pretty-awful paper I got from the University where I used to work which was made into small square pads. It's probably 90GSM. Soaked for 30 minutes then rinsed and dried.
The biggest surprise came from the Pelikan 4001 that was in the long cartridge - it still retains most of its colour, unlike my favourite bottled version. However, that pen was filled some time ago so could be a little 'long in the tooth' - a bit like me! The Platinum stayed true to form, being visually really a 'dark blue' and the Pilot is a little paler.
Edelstein & Sailor are about right - somewhat blurred but reasonable legible and would probably behave better if only subjected to a liquid spill. The 4001 Violet was only included as I've recently inked a new addition with it and haven't really done this test on it before.