See an example of vertex colored skull from MorphoSource. https://www.morphosource.org/concern/parent/000101191/media/000358488
These were derived from CT scans, which are also available on M/S, but the segmentations are not. Would it be possible to import this model in a way that each color is a separate segment? Right now, it is importing everything as one element.
Some coding would be required, but the mesh could be split based on vertex colors and if they are closed surfaces they could be converted back to filled regions in a volume.
Inthimk you cannuse vtkPolydataConnectivityFilter for that using your color scalar as one of the arguments.
Then do a for loop of all componnents and use a vtkthreshold, wirh the geometry filter at the end.of the pipeline
Hope it helps