So I know that a concentrated form of Fire Ink can be used to produce a tattoo that glows and flickers as a flame and won't fade. Can Glowing Ink be used for a similar purpose, and does it have to also be concentrated, costing 10× as much?
Neither Adventurer's Armory nor Ultimate Equipment provides any information beyond what's included in the Open Gaming License version of glowing ink. Glowing ink appears to be usable solely for writing script or composing illustrations that glow (therefore making items that have been tagged up with glowing ink more easily found). Glowing ink is not mentioned as being usable in tattoos, despite the description of tattoos—also present in both books—mentioning that they can be done in a variety of colors. There's just nothing said about the possibility of glowing ink tattoos.
The Advanced Race Guide on the ifrit on New Racial Rules says, "The following options are available to ifrits. At the GM’s discretion, other appropriate races may make use of some of these new rules." That section is, in turn, followed by the subsection Ifrit Equipment that also has a short description: "Ifrits have access to the following equipment." Then that subsection describes fire ink and ifrit's blood. Thus, because of its unique placement in the text, this reader is led to believe that fire ink is supposed to be a bit more special than everyday ink or even glowing ink, and one of its unique properties is that it can be used to make awesome tattoos.
With this in mind, this reader would read this to mean that, technically, No, a creature can't get a glowing ink tattoo. However, since glowing ink doesn't provide enough light for the creature to see by normally or anything—instead glowing ink only illuminates what's been depicted in glowing ink—, this GM would rule that Yes, a creature can get a glowing ink tattoo. That is, this GM doesn't foresee any balance issues with allowing a creature that wants a glowing ink tattoo to get one. (In fact, this GM can imagine several significant disadvantages to having one!)
Nonetheless, determining the price of a glowing ink tattoo is difficult as ink typically costs 8 gp per vial (or 16 gp per vial in colors other than black) and glowing ink—for reasons that baffle everyone—typically costs less than normal ink at only 5 gp per vial! (Note that ink and glowing ink are sold by the (presumably) 1-oz. vial—and, so you know, one Paizo forum post estimates that's enough ink for well over 100 pages of text—, and fire ink is sold by the 1-gp dose that "covers an approximately hand-sized area," but that same amount of tattoo-ready fire ink costs a whopping 10 gp per dose. What exactly all these details mean to the aspiring tattoo artist or subject I leave to the frustrated and overworked GM. I'm sorry.)
Anyway, it seems like a glowing ink tattoo should cost more because it glows, but, apparently, such a tattoo may have a price about 35% less than a normal ink tattoo… if the only cost involving the tattoo is the ink. (Pro Tip: It's usually not.) Still, a glowing ink tattoo may not be to everyone's taste: the only colors of glowing ink that may be available are red and green. (According to its description, glowing ink is usually red or green; other options aren't given prices or availability and are therefore up to the GM. This GM would likely have other colors cost twice as much—just like normal ink—because, really, why not? Especially since that means a creature can get extra style points for a glowing ink tattoo done in black glowing ink!)
Note: Glowing ink can be combined with marker dye—the combination having a price of 20 gp—, and the combination can be used as splash weapon. When so used, it can't be washed off for three days then lasts for two weeks if it isn't washed off after those first three days. So this GM would totally allow a creature to employ the combination to, if it wanted to, test drive a glowing temporary tattoo.