From what I remember when I worked at
http://www.bios.edu/ back when I was young,,,,,,, was that they changed color to hide, they were amazingly adaptable to look just like what they were in front of.
But they also had color changes when they were threatened or 'angry'.
We had some in our labs as 'pets' for a while, then we always let them go.
But what I loved was when we were diving and the water was relatively calm, they would come up to you in a line of perhaps 5 or 6 of them and just LOOK. Like a human looking into an aquarium, they were looking at me with my diving mask probably looking very strange to them but not threatening. Of course I held as still as I could and my bubbles didnt seem to distract them.
Sure wish that had been the digital camera age, but its all in my memory.
Im too old to scuba any more, but my memories are great.
Squid are really colorful too, and they are wonderful to watch. They act a bit like each other.
Glad you put this link up, brings back some lovely memories for us.
Jane