Kudos for doing the research ahead of time! So much better than jumping in without thinking things through all the way!

I am not overly familiar with the American Green tree frogs, but my 4 Red Eye tree frogs vary in color depending on if it is night or day and during he day their color varies based on what they are sleeping on. I have seen them go from Bright green in the daytime to a blueish or purple color. At night they turn dark green so they blend in better in the dark and hunt crickets

I ended up switching form traditional bulbs to LED lights. I had issues with the standard bulbs killing my humidity to much. I also switched from a heat bulb to a Ceramic Heat Emitter. I absolutely love it! Having a variance between your night and day temps is actually better for your frogs. It will simulate the temperature of their environment much more accurately.