Hence: the Photoshop color comp. If Gustave Baumann had had Photoshop (and was under 60 at the time...), he woulda used it instead of doing a whole gouache painting to organize his process. Not that doing a gouache painting as a preliminary organizational comp isn't extremely cool and something I plan on doing myself...
The black you see in the image is a scan of the actual black keyblock, though not the final carving. Other color added in Photoshop. Each of the five layers has one to two ink colors that aren't touching and are separated enough that they can be inked w/ a small 1.5" brayer, if necessary. The light lavender layer is actually transparent, and reflects that I'll be using a lot of ink base extender to get that kind of transparency on the block. The dark green layers under the boat will be rolled and brushed out to get that gradation for each print.
Yah, this is kind of nuts.
Original image credit: © Michael Jones 2011, photographer.