Worth ruling illness in or out since he has been dark for days: a sick anole often stays dark and loses the ability to change colour at all. Come in if there is lethargy, no eating beyond a short gap, weight loss showing as visible hips or a thin tail, swelling, sores, stuck shed, or trouble climbing.
And check the husbandry trio while you have the lid off: UVB with a proper day and night cycle, reasonable humidity, and misting daily so he can drink droplets off the leaves rather than expecting him to use a bowl.