What drives the color change in green anoles?

There have not been previous studies investigating whether red causes stress, but the color of the Green Anoles dewlap is red. Often times, when males extend their dewlap during aggressive displays, this results in the formation of an eyespot in both anoles. Eye spots are a well known indicator of stress in anoles, hence the red on the disk should replicate the stress an anole would feel if receiving an aggressive display from another anole. Even despite the color, a large disk moving quickly towards the anole is sure to stress the lizard, as they dislike sudden movements towards them (it is likely similar to what they experience when being attacked by a predator). It is not of interest to do a color examination while the anoles are sleeping, because I would only be able to test color and not stress (otherwise they would not be sleeping). In addition, the thermoregulation hypothesis would not be able to be tested because there would not be light levels to influence (the lights would need to be off if they are sleeping). The ambient temperature will remain constant, and is not a factor when testing either hypothesis. Thank you for your interest in my project and all of your support! If I did not answer all of your questions, please feel free to comment again.