Everyone knows that octupi change color. The theory behind why this is is because this allows them to camouflage. However, I heard from a source that this is also used to communicate - that one octupus can go through a quick series of color changes and another octupus can see this series and confer a meaning from it.

It's used in courting and also as a sign of aggression, I'm not sure what else.

 

Eg courting: http://www.cephbase.utmb.edu/viddb/vidsrch3.cfm?ID=133

I imagine it's the same as any other animal that interacts with others of it's own kind... as it's underwater it can't use audio methods so has to use a visual one.

Actually, underwater life is extremely vocal, I've heard it compared to the unending calls of birds and monkeys in a rainforest, it just happens that we can't hear it ourselves.

 

Octopus really are amazing with their color change, but its foremost function seems to be camoflauge, or in some cases, such as the mimic and blue-ringed octopi, is used to discourage predators.

 

To really see complex, dazzling displays for almost pure communicative purposes, look at some other cephalopods, most notably the cuttlefish. Those things are just insane.

Gib65,

 

There have been some pretty interesting shows on this recently on the Discovery Science Channel. I can't think of any of the names, but if you have the channel keep an eye out and I'm sure they'll come around.

I know they communicate on basic levels...warning of danger / aggression et.c however they're the most intelligent of all molluscs, and apparently as intelligent as dogs. So to have a more subtle form of communication using colour (which we're yet to decode) seems pretty plausible.

 

Agreed, cuttlefish are also awesome.