Your mention of shifting color patterns in Cephalopods reminded me of an
interesting experience a couple of years ago.  I was doing some intertidal
collecting up at Manomet, near Plymouth, Massachusetts.  It's a typical cold
water, rocky tidal pool habitat.  In one little sand pocket among the rocks,
containing perhaps two or three cups of water, I noticed a sort of sparkling
or iridescence in the water.  Even when I got my face right down there, I
couldn't tell what I was looking at.  I scooped up a double handful of
water, and the water in my hands continued to sparkle with multicolors.
When I got the light just right, I could see that there were tiny, almost
transparent organisms swimming around in the water.  And they were pulsating
(that's the only word that describes it) with ever-changing iridescent color
- blue, green, red, and what I can only call silver and gold.  It was just
fascinating.  I still couldn't tell what they were.  Finally I let most of
them trickle back into the water whence they came, but a couple of them
stuck to my hand, and once they were out of the water I could see that they
were newly hatched squid (probably Loligo pealei, our commonest local
species).  Each one looked fully formed, with fins and tentacles, and each
one was about 1 cm in overall length.  I wished I had my camera, but it
would have been difficult to shoot, and besides, a still photo could never
have captured the effect of colors coming and going, changing from one hue
to another.
Paul M.