What feeling often causes the Green Anole to shift to duller brown?

Feeling chilled, stressed, or aggressive

The ability of anoles to change color via specialized chromatophores is often assumed to be solely for camouflage, but this is a common misunderstanding. While blending in is one function, rapid shifts to darker coloration, specifically duller browns, are strongly correlated with the lizard's immediate physiological or emotional state. A lizard that has cooled down, perhaps after a cold night, will darken its skin to maximize the absorption of solar radiation while basking in the sun to raise its body temperature efficiently. Similarly, heightened states of internal arousal, such as feeling stressed or displaying aggression toward a rival, can also trigger this darker hue.