I work in printing and although its probably not the same thing used in bowling balls, the inks we use will come off or stain in varying degrees based on the color. Blues, Purples and Reds tend to be the world worst about getting off, often times they won't at all, its just not as bright.
My guess it has something to do with the type of coloring agent they used on certain batches, or whatever drying/hardening agent they used didn't blend as well and its allowing certain chemicals to re-wet the dies.
Often times if I miss a spot of ink and then go back a day or so later after its dry and hit it with alcohol, it will become wet again and wipe off. Wouldn't surprise me at all if a version of the same thing isn't happening.