It'd been a minute since I bought a new pen, and I've always wanted to try a vacuum fill pen so I finally pulled the trigger. The pen writes so well straight out of the box but that's always been my experience with TWSBI pens. The kon-peki ink is a nice beautiful blue that also seems to dry fairly quickly which is nice because I'm a lefty and it's impossible for me to write without making a mess lol.
I like Iroshizuku ink a lot. I have a bottle of Shinkai ("Deep Sea") that's a nice blue-gray (more gray than blue, though).