Are you adequately soaking the coconut fiber before putting it in the tank? It should be moist but not soggy. I think the reason it is drying out is because of the undertank heater which I dont believe is needed for these frogs. They thrive in moderate temps and humidity, nothing extreme. If your moss is dying it is probably because it it too dry. If you want their color greener you just need to have greener surroundings. Maybe try one side with green poster board instead of black. My frog is always a darker gray despite the greenery so sometimes they just are what they are.