I have always had a fascination with Chameleons ever since I was little. I was really excited when we talked a little about ecototherms and how they can mimic their surroundings. I never knew how the ability to change color worked so I took this as my opportunity to research it a little.
First thing I found was ecototherms , chameleons, cephalopods, octopus, squid, some frog and fish, are animals that can’t generate their own body heat in the same way as mammals and birds. They also have specialized cells that allow them to change colors. Those cells that contain the pigment are called chromatophores, which are a big part of skin color.
In vertebrate ectotherms like my little chameleons there are three main chromatophores; Xanthophores which contain red and yellow pigments, melanophores which contain the black melanin, and iridophores which contain stacks of crystals that reflect and scatter light to generate hues. The melanophores are a big part of the color changing process. The process occurs when a group of melanin pigment moves within the melanophores.
The skin looks pale when the pigments are still in the center of the cell, but when they begin to move within the cell the skin appears darker. The color can also change when the spacing changes in the stacks of crystals within the iridophores. This affects the way they reflect and scatter light which changes the color.
“Triggers” like light and temperature can cause quick color change. This is why chameleons look pale when they are sleeping but become dark when a light is shone on them. They are also very dark when cold because black absorbs light and lighten up when warm because light colors reflect light.
Check this site out for more info about chameleons and cephalopods.