They are equally curious about other cuttlefish - even images of cuttlefish - as the video below by Brian Leahy demonstrates. In the middle of the video, the videographer turns the camera's display around to face the nearby cuttlefish which inspires an immediate darkening response, and causes all the other cuttlefish in the tank to start moving purposefully toward the camera.

An article by Brenna Lorenz describes an encounter with cuttlefish and humans who had the idea to match the gestures made by the cuttlefish with their tentacles. The Cuttlefish of Sentosa (Sentient Cephalopods), by Brenna Lorenz

In a similar vein, a comment on a Reddit story on a troublesome octopus describes how the author, Saydrah, used hand-signals to communicate to a tank full of cuttlefish:

"...Okay, I was 13 and on a school trip to the Monterrey Bay Aquarium. Each kid in the class had been assigned a sea critter to study, and mine was the Cuttlefish. I realized while writing my report that in almost every photo of a cuttlefish where it was clear that it could see the person taking the photo, it held its tentacles like this. (click here) I was also learning some sign language at the time, and it clicked: It's a greeting. At least, that was my theory, and as soon as I got to the aquarium I sought out the cuttlefish to test it. There were 16 cuttlefish in the tank. I asked a staff member about them, and she said, "I know we put 16 in there, but they blend in so well we haven't seen more than 6 at a time since then. There haven't been any bodies, so I presume there are still 16." At first I could spot two, camouflaged on rocks. I went up to the tank, knelt down, and held my fingers in the greeting pose from the photos. Incidentally, cuttlefish have 10 tentacles, two of which are set back and only shoot out to grab prey. Much like 10 fingers with two set back thumbs. It's easy to make your hands into a recognizably cuttlefish like shape. With 10 minutes, I had 13 cuttlefish lined up at the front of the tank doing the greeting pose back at me. My teacher got all this on video, and a couple staff members came over and were floored at the sight. They started doing the sign language at the cuttlefish too, and the cuttlefish responded to them also. Some of them also changed color, which obviously I couldn't mimic, and made different tentacle poses, which I tried to repeat back to them. After a couple minutes, one smallish cuttlefish turned red, grabbed a shrimp that was in the tank as a snack for the cuttles, and pushed the shrimp up against the glass in front of my hands. It seemed to be offering it to me. Then a larger cuttlefish turned white, grabbed the shrimp from the smaller one, and the big cuttlefish then repeated the effort to push it through the glass to me! The small cuttlefish turned gravel patterned, shot a jet of water out, and went to hide behind a tank decoration.

from comment by Saydrah on Reddit

The ability of cuttlefish to instantly mimic the color and texture of their environment, particularly the area underneath them, is well known but little understood. They use a layer of chromatophores and a layer of iridiphores (reflective cells) [Meet the Cuttlefish] which are revealed when chromatophores contract as well as detailed muscular control to create visual and textural illusions.

The textures and colors they imitate are so complex that it led me to wonder if cuttlefish use only their eyes as the sole inputs for processing visual information. In other words, if their eyes are covered, can they still mimic their surroundings? Several recent articles present evidence that their eyes are indeed the main sensors. Cuttlefish eyes have been determined to be colorblind, but are sensitive to the orientation of polarization of incoming light. One study determined that contrast is one of the main visual cues used to determine the pattern of camouflage.

Cuttlefish mimicking a net trap
(I don't have an attribution for this photo yet)

Their visual patterning is used for communication as well as camouflage, and even sometimes for hypnotizing their prey [ A Dazzling Show.]

These visual signals have been analyzed and found to have a signal capacity of approximately 3 bits per signal - enough for some primitive communication, if not an actual language in the human sense of the word.