I have Noodler's B-B and Namiki/Pilot B-B.
N's B-B is darkened with the N's Black dye, which when diluted is brownish, so combining it with blue makes a slightly greenish B-B. I still love N's B-B

! My water test of it left an impressively legible result, too.
I also like Pilot/Namiki B-B. It's a very opaque, pastel blue with some gray, it's the second-bluest B-B in Greg Clark's
Sampler, it doesn't have any hint of green, and his swabbed sample in my copy matches the output from my Pilot Vanishing Point M written right next to it. It's bluer than some blues in the book! It's also extremely water-resistant and therefore envelope-address-worthy. I think the Pilot/Namiki marketing folks, by selling this color only in their proprietary cartridges, are missing the opportunity to compete more in the water-resistant market niche. They already have an excellent bottle.
N's B-B is much better-behaved in "bad" paper than P/N B-B.