New segment for every colour

[lassoan (Andras Lasso)]

It sounds like you have a labelmap volume (you have discrete values in the volume, each value corresponds to a certain structure). You can follow these instructions to load this image and import to segmentation:

Save .nrrd file into STL file

If your nrrd is binary (i.e. contains a segmentation) then you can load it as a labelmap (click Show Options in the load window and check LabelMap option). Then go to Data module, right-click the labelmap, select Convert labelmap to segmentation node. Then go to the Segmentations module, select the segmentation, go to the very bottom to the Export to files section, then select your options and click Export.