OCCT 7.7.2 seems to come with IGES import issues:

I tested with v7.7.0 and we are able to correctly import the sample file (please find sample file attached).
We expect the sample file to come with colors, but with 7.7.2, there are none.
I think that the issue is related on how OCCT reads sub labels. The same file but in STEP format (converted using CAD assistant v1.6.0) is properly read, and colors are displayed.
If you see the stepPlaneTree.png (attached file), you will see the hierarchy that should come.
In this case al sublabels like [0:1:1:2:1] are the ones that contains colors., but with last OCCT versions, seems that they are never processed.

Kind regards,
Lorenzo Navarro