A quick peek let me see a faint outline, so I used some Iced Spruce color distress ink spray on the edges of the soaking wet paper and let them sit awhile still clamped together. When I opened the packet this is how they looked. Distress inks are so reactive with water it spread all through the packet.
The second packet I returned to the pot and poured in more of the distress ink right into the pot and let it boil for another 20 minutes. When I removed them, of course the water was now darkened more, and so was the paper.
I set this packet on a tile and let it sit overnight with a stone on top to keep the pressure on the leaves.
This is how they looked when I peeled them open. You can see most of the color is gone from the leaves, but hardly any migrated to the paper.