so I just bought a leopard gecko (It's my first reptile) and last night I had turned off it's heat mat. I had read that leopard geckos could withstand temps of 70s (which is the coldest it usually gets in my house). But this morning when I went to go feed it, it was pale and cold to the touch. It's alive, and it caught two of the crickets I put in the tank, but I'm worried for it's health. It's a juvenile leopard gecko.
I do not know a lot about geckos, but my turtle is a poikilothermic animal too. They need the warmth to get going. If they have a low body temperature, they cannot move fast or with much power. So they need a place to warm up (for my turtle this is the sun-like light bulb on his island) to become fit, i.e. to hunt.
My turtle has his light shining at the daytime only, but the water has thermostat so it stays at the moderate temperature all the time.
A good way to let your animal choose its body temperature itself is to provide a temperature gradient over the animal's space. For example, provide the heat mat on one side of the terrarium and a "cold spot" on the opposite one. With such an arrangement, the gecko can choose the distance to the warmth, and thus the temperature, according to its needs.
If he/she is grey or white, that could be a sign of shedding. It's not worrying - but having lasted for so long, it's probably not good.
As for the heating, problem I am not sure about babies - but an adult, average gecko's temperature during the daytime should be 24 - 27 °C (75 - 80 °F). I don't know about night temperatures; I own a leopard gecko and she is fine with her cage being 26 °C (78 °F) at night. By the way, I count ferrinhight.
Best of luck to your gecko.