Finding the perfect ink is hard. I by myself am on the search for the perfect dark, deep blue. I went for Asa Blue, Majestic Blue, Sargasso Sea and Oxford Blue in 80 ml flasks. My free samples are Sapphire Blue and Midnight Blue.
For my use (dark, deep blue) I like Asa Blue the least. It's too bright for my taste and has lots of green in it.
Majestic Blue and Sargasso Sea are the ones I like the most so far.
What is sure, however, is that I'm going to test every single one of them out in the office for a few days each and see how it goes.