I'm getting a new meer soon, and I'm going to make my own coloring bowl. Here's what coloring bowls are. Click through the thumbnails below the big picture.
Basically, they work on unsmoked meers because by moving the combustion to a separate bowl, the walls of the new meer (which is porous) don't get clogged. This is why the shank always colors first on meers when smoked normally; there's never any combustion clogging up and blackening the walls of the shank. A coloring bowl turns the entire pipe into a shank. This is also why coloring bowls are no use to a pipe already smoked.
Now, I'm not going to carve one out of meer - no sir. I'm DIYing one from a Missouri Meerschaum bowl and a wine cork. Meerschaums are pricey enough, there's no advantage to a meer coloring bowl, they're expensive, and cobs smoke great and are cheap enough for me to cannibalize for this project.
I'll be posting pics of the construction and the coloring process along the way.