I'm disappointed to have to let you guys know that Prismacolor pens are not really permanent when it comes to using a water-based product in the joint lines of resin brick! The ink will dissolve and discolor your joint mortar (thin acrylic-based paint). The only pens that I've used that remain impervious to water are the Tria pens by Letraset, which use an alcohol-based ink. I don't know how they can call Prismacolor permanent when you can't get it wet!
Frank
Sorry to hear about that. I will be painting brick pretty soon and am always looking for new tips and tricks. Thanks for the heads up.