Hello Michał,
The answer is actually shown in the command line of your screenshot image!  You would use the “volume” command to set levels and colors.  Instead of a color name you could give r,g,b,a  values (red, green, blue, alpha=opacity, each on a scale 0-1).  Just like you can say “level” multiple times in the same command, you can also give “color” multiple times.

<http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/midas/volume.html#general>

I hope this helps,
Elaine
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Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Nov 16, 2017, at 6:22 AM, Michał Kadlof <m.kadlof@cent.uw.edu.pl> wrote:
>
> Hello,
>
> how can I achieve the effect visible in attached image from command line?
>
> I need to add several semi transparent isosurfaces for a single volume.
>
> <Zaznaczenie_139.png>