Detection of Voice Number

[Urs Liska]

Hi all,

one more question about processing output:

I would like to test each note and rest for the Voice number it has.
Then I would like to set the color of this note/rest and corresponding 
grobs (Stem/Flag/Beam) to a color depending on the voice number.

Unfortunately I'm stumbling quite hopelessly through the IR, thinking I 
could get somewhere with ly:context-property but not knowing what the 
property name of a voice number (or generally the properties of a Voice 
context) could be or where I could look this up.

Any hint is appreciated
Urs