Geckos, like all other "cold-blooded" animals unable to physiologically regulate their own temperature. The thermal images below (reproduced here with kind permission from NASA/IPAC/SIRTF) demonstrate that geckos, being "cold-blooded", take on the environmental temperature- notice how the gecko is always exactly (or very close in colour) to the colour (i.e. temperature) of the background air in each of the images. You can see how cool the gecko is in comparison to the "warm-blooded" human holding it. The gecko's eyes are the coldest part.