I also have noticed this however, some translations keep the color information. If igs doesnt, try stp (as i know color information works better with one vs the other but which way I can never remember). I would also play with solids vs. surfaces (most models I deal with are surfaces ...)
I have not been able to find the exact setting, and my research has not yielded much in the help docs. However, my former employer had IGES files, either surface or solid, that would retain individually colored faces. (from V5)
Now, I'm not sure where the setting is - but have you tried selecting individual surfaces, or are you trying to carry over colors that are selected on the Part Body?
I just did an experiment, and mine retained color information.
I had six surfaces - 3 blue, and 3 yellow, on a solid part. (functional surfaces) I had manually changed color on each individual surfaces.
My iges output is set to solid body.
I have R12-R15 installed on my machine, and it works flawlessly in all versions.
You should contact your admin, because I can't even find a setting for this. I thought that color was always recorded in the IGES output, but I'm not an expert on the subject.
I just found the following APAR on the IBM Tech Support page
Software > Applications - Desktop & Enterprise > Product Lifecycle Management >
HD45759: IGES / SAVING TO IGES FORMAT DOES NOT TAKE INTO ACCOUNT COLOR OF THE SOLID.
THIS PROBLEM WILL BE FIXED ON CATIA VERSION
5 RELEASE 17 GA level.
NOTE THAT THIS PROBLEM WILL ALSO BE FIXED
ON V5R16SP02 AND V5R15SP05.
APAR information
APAR number HD45759
Reported component name CATIA V5 NT>XP
Reported component ID 569151000
Reported release 515
Status CLOSED PER
PE NoPE
HIPER NoHIPER
Submitted date 2005-10-20
Closed date 2005-11-22
Last modified date 2005-11-22
Quite recent APAR I guess it 515 relates to V5R15 I assume GA code
Sorry that I can't be of more help to you, but I guess, like you said, it may be erratic. I'm just not seeing the problem.
Great question, by the way. The color is important, especially when considering interoperability - such as trying to highlight a specific problem area for someone who is working on another CAD system. I immediately understood the value of your question, as I rely on this method to get my point across.