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.
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