[Phlogiston]

The Behlen Pore-O-Pac stuff is grey. Best that I can tell it is clay in an oil based solvent. I have used it. It fills very well. It must be tinted prior to use. The only problem I have had with it is, once tinted, the color transfers to the wood. A very careful sanding will resolve this, however aggressive sanding will remove the filler from the pores.

You can't use this stuff as is out of the can unless you are going to paint the surface.

Not recommended for people not accustomed to tinting paint.