I'm not sure if there's a dedicated script geared towards this, though I know it can be done (relatively) simply in the Material room. Just place an hsv node between the root and any coloured image, and set saturation to zero. Do this with the lights as well (transcribe the light colour to a colour math node, then push it through an hsv and on to the root). Posework's Shader Spider would let you set up a wedge shader like this (where you break apart an existing shader to add in extra materials), but that has not yet been updated to Poser 7. It should be possible to write a dedicated Python script to do this, but I'm not the fellow with the know how to do so.

Now that I've spelled out how to do it though... any takers?

jonthecelt