A bit of searching found a fly-tying site that stocks "prismatic
markers"
http://store.theflyshop.com/catalog/product_info.php?products_id=4210.
Looking closely at the image, they are Prismacolor brand but not the
pencils, instead they are double-ended wet markers.

According to the Prismacolor site
http://www.prismacolor.com/sanford/consumer/prismacolor/product/catalog.jhtml
they use alcohol-based dye ink.

Thanks for finding this. So, they are in the art marker busines now, too. It is
very likely that those dyes are fugitive, so be careful. Now that I think of it
I recall seeing some of my students using these. I preferred another brand,
using xylol/alcohol. Art markers are intended for sized paper. We left the caps
off overnight so they'd dry out some and wouldn't be so juicy. That gave them
the ability to blend and gradate. To each, his own. Dan