[wierdaaron]

Any art or writing instrument store will have gobs or pens and pencils (or lead inserts for mechanical pencils) in this shade of blue if you're interested. As the article states, it's good for sketches that you'll ink or pencil over later, since they will disappear if you scan or photocopy them in high-contrast B&W.

It sort of reminds me of the old graphics method of using RGB(255,0,255) for sections of a sprite that should be transparent, since an alpha channel wasn't an option, because it's such a hot pink and such a precise color it would never naturally appear in artwork.