I use the black fine point pen to write in the margins of the Bible and the blue one to underline Bible verses. It's the perfect size to fit between the verses of my HCSB Ultrathin Reference Bible! I love the color. I use a bookmark to make a straight line when I underline and enjoy that the color is easy to find when searching for an underlined verse. Sometimes I go over the underline one more time if I wish for the color to be a little bit darker. It dries in seconds and does not bleed through, though you can see the ghosting of the markings on the opposite page. These are wonderful pens and I plan to get more colors!
I have been using this Pigma pen on my ESV Study Bible a for years now. It's great for underlining, circling key words, drawing faint lines connecting key works to each other, connecting my notes in the margins to key words with faint light lines, making notes from the sermon. It personalizes my Bible and helps me remember insights learned in previous years. I prefer blue color the best because it stands out from the black print in my Bible without looking strange like a pink color would in a men's Bible. It does not bleed through or fade.
By the way, I use a separate, different ergonomic gel pen* for fast and easy notetaking in my sermon notebook** (not Bible), and save the ink in this Pigma pen for my Bible only.
*Pilot G2 Limited Retractable Gel Ink Roller Ball Pen, Fine Point, Black Ink, Gold Barrel (sold elsewhere)
**Five Star Spiral Notebook 6x9.5", which fits inside my XL size WordKeeper Bible Cover (Christianbook.com)
That's my system.
I'm surprised about the reviewer who said "Not for Bibles". I don't have a problem with it bleeding through. In fact, the very reason I buy these pens is because they don't bleed through Bible paper. Perhaps the reviewer below does not want to even see anything from the other side. I'm not sure if there is any such pen or pencil like that. Bible paper is thin. You can even see printed type from the other side if you hold it up to light. I think this Pigma pen is the best for Bible paper and don't see where it "bleeds through" at all. But yes you can see through Bible paper to see printed text on the other side, or underlining, if you underline deep thick lines on the other side of the page. I wouldn't call that "bleeding through". My whole ESV Study Bible is filled with notes and underlines with this pen. It's great!
This pen does show through the onionskin paper that the majority of Bibles are made out of. It is the same kind of pen you would find in a Scrapbooking supply store. Great for writing on card stock...not for Bibles.