BOMApens come with blue ink, fine point, genuine Cross® cartridges.

Cross® cartridges were chosen for three properties. The first two are generally important: they work very well and are readily available. The last property is more esoteric: students of human nature know that people gauge a combination of density and weight when they heft something. In other words, if you pick up two objects with exactly the same weight, the smaller one will feel heavier. BOMApens are dense but are actually only a little heavier than the much fatter pens you commonly see. If BOMApens had been made with standard tubing technologies, the extra density oomph of tungsten would have been diluted to bare perceptibility. Instead, to enhance their net density BOMApens are kept as solid as possible: they're machined from solid bars and they use the slimmest and longest (high quality) ink cartridge available–the Cross cartridge.

A fine point tip was chosen to complement the pens' precise feel and look. Excessively active marketing personalities also say things like this so let me explain:

The look of BOMApens is undeniably smooth, clean and modern–the pens don't even have clips (trust us, you don't want one of these in your shirt pocket). A fine point is the sharpest and completes the shape of the tip most aesthetically. Please note that fine point cartridges are not actually the smoothest writing. Larger points have bigger balls which move over paper texture with less friction. The tradeoff is that the bigger points obviously leave a wider swath of ink that makes letters less legible. Predictably, we chose precision and aesthetics over smoothness for the pen's first cartridge.

The precise feel of BOMApens is really, truly there for anyone to experience. Most ballpoint pens have their cartridge tips coming out of holes that are typically bigger by 5 to 10 thousandths of an inch (.005" to .010"). This might not seem like much but consider that written letters are roughly 100 thousandths tall (.100") so the wiggle from right-to-left and up-to-down is roughly 5 to 10% of a letter. This is the "slop" between what you write and what actually gets written. Small features like the hole in the letter 'e' are only about 15 thousandths tall if they're cleanly legible. So the slop in a regular pen is not insignificant. BOMApens have tip holes matched to the cartridge tip within one thousandth of an inch. So they do, infact, feel precise because they are precise. We hope you like that.

Few cartridges maintain the level of precision required to accurately fit BOMApens. Please don't bother with Brand X refills. They are usually noticeably smaller and therefore, sloppier. We are also unwilling to vouch for Brand X inks' dry-out resistance, color, lubricity, or ball abrasion resistance.
Incidently, the balls of Cross ballpoint pen cartridges, like almost all quality ballpoint pen cartridges, are made from tungsten carbide the same material that most machine tool bits are made from and BOMApen bodies are sheathed with.

BOMApens come with blue ink because blue ink indicates that your signature or writing is an original, not a copy. Many legal documents require a non-black color for this reason. Interestingly, red is also often not allowed because of color blindness considerations (not seeing red).
How times change. Ink was once blue by default; it was "India" ink. More recently, blue ink was favored in part because copies were black being as they were made by carbon paper. Then came blue and red and other colored "carbons" and black ink became cool. Now carbon paper is gone and Xerox copies are black, so blue ink is in again. I wouldn't loose sleep over this, but color copiers are becoming ubiquitous so we're going to need a higher tech marker for original ink soon (maybe fluorescence?).