Namiki Blue is an understated ink that not a lot of people are familiar with, but it is a great option! A nice, dark, pure blue, and very water resistant. My review here is probably showing a lighter color than what this will show in an non-stub nib. It has a red sheen when used with a more wet writing pen in conditions like Diamine Majestic Blue and PR Electric DC Blue.
If you're not a big fan of the extended dry times of wet inks this may just fit your bill. It has a tendency to coat the feed of your fountain pen due to the heavy red sheen. No harm, really, just more work to clean. Namiki Blue a nice looking and working ink I can easily recommend. Check that out here.