Check out those chromatophores! Some large, some small. Some round, some angular. Some on the upper surface, some below.
In the next photo, you can see one of the gills pretty clearly. Look for the ladder-like structure hanging in the lower left portion of the mantle.
Most of the octopus showed predominantly red pigments. But a few were noticeably yellow (see especially lower animal in next image), and eventually I learned that I could track these individuals easily.
Who knows if we'll ever get to see octopus of this size again, but I'm glad to have a few pictures to remember what they were like!
P.S. For anyone who missed them, earlier parts of this story are here (hatching) and here (development).