Tom Kuwahara and I have had the same problem, if you press too hard
to get the goo started with red pens,it will express a puddle!
of red sludge on the slide.  On looking at my pens, the 
manufacturer is written on the side, Kiyota.  If this is the supplier
to many vendors, then the red color WILL leach into solvents and
mounting media and I have slides and an array of colored solvents to 
prove it.  The clear pens are different, they seem to go onto the slide
with different thickness or layer of goo, do not flow as easily as the colored
pen.

I assumed the pap pen is a trademark and one company makes to pen for
everyone, any comments? just changes the label for vendor accordingly.
Much like Erie does for their slides for Fisher and VWR, etc, etc.

Still looking for the perfect hydrophobic barrier slide, plus charged,
for a multitude of IHC.  

Gayle Callis