Filament Dye - Cheap and Simple

So, I was printing some bar clamps for the Prusa Mendel and an odd idea popped into my head and before I knew it, I was rubbing dry erase marker on the filament prior to printing. About half way through the build I noticed that the filament being laid down was changing color. It appears as though the filament is being extruded without any halt, error, or otherwise. The dyed filament adheres to the HBP of my Thing-o-matic just as regular filament would. The layering is identical, and no other errors or anomalies were visible. I am not encouraging anyone to do this due to the fact that I do not know if any residue remains in the extruder mechanism, or if any damage is being done to the machine. More testing will be done to see what is going on in terms of damage, fume addition, etc. This can be a very cool , and cheap way of dying filament especially pink which is expensive as you all know. I am using Expo low odor dry erase marker. I have only tried purple, black, and green. Purple come