Hi pymol-users

I have previously been able to make quite nice visualizations of my volume object, containing the time-averaged density of atoms from a MD-simulation.
For making even more improvement, I'd like to be able to use a script (either python or pml) to control which regions of density gets which color. 

I've found this thread 

http://www.mail-archive.com/pymol-users@lists.sourceforge.net/msg10294.html

that suggests it to be possible, but understanding how to use that for my case is unfortunately (yet) a bit beyond my current pymol-skills.
Ideally I would want to have a solution that allows me to load in my volume-file (in .dx format), assign colors to different regions of density systematically (the Volume-GUI is great, but somewhat tricky to make quick changes with), and display the result on screen.

Is such a thing possible?

Thanks
/Per