One researcher has seen "communication" in one species of octopus, but it's mostly looking big and dark to drive away others, or small and light before being driven away[0]. It's a very primitive communication, like rattlesnakes do to scare away dangers. Not the kind of complex system I was thinking of.

I'm being very human-centric, though. It just seems like if they're intelligent enough to recognize individual faces, use tools, and learn from what other octopi do, a complex language would be inevitable. And from there they'd accrue oral histories and localized cultures.

[0] https://www.livescience.com/53514-octopuses-lead-social-live...

I highly recommend the Netflix documentary ’My Octopus Teacher‘. This is the story of a photographer diving everyday for a year, and developing a two way bond with an octopus.