Following up myself on this. I did some more digging on Google, and putting together bits and pieces this is what I have currently.
It works, but does not (yet) allow me to scale the colors according to eg. the max and min values of my density (which I do not know how to access).

I guess that means I have a new question about accessing details about the density-object.

Thanks
/Per

load density.dx, d
cmd.volume("density","d",1.0)

bg_color white

from pmg_tk.skins.normal.ColorRampModel import ColorRamp
r = ColorRamp(nColors=256)
r.addColor(0,(0,0,0,0),0)
r.addColor(2,(0.39,0.67,1,0.01),0)
r.addColor(130,(0,1,0.50,0.25),0)
r.addColor(192,(1,0.0,0.0,0.25),0)
r.addColor(255,(1,0,0,0.25),0)
ramp_colors = r.getRamp()
cmd.volume_color("density",ramp_colors)


21 nov 2012 kl. 17:30 skrev Per Larsson:

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 
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