The actual gs documentation says: The tiffsep device also prints the names of any spot colors detected within a document to stderr, (stderr is also used for the output from the bbox device). For each spot color, the name of the color is printed preceded by ‘%%SeparationName: ‘. This provides a simple mechanism for users and external applications to be informed about the names of spot colors within a document.<
But output is not showing this.
gs -sDEVICE=tiffsep -r100 -o out%03d.tiff test.pdf GPL Ghostscript 10.02.1 (2023-11-01) Copyright (C) 2023 Artifex Software, Inc. All rights reserved. This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY: see the file COPYING for details. Processing pages 1 through 2. Page 1 Page 2