Welcome.
First thing would be to let the new frog settle in.... this could sometimes take a month.
They are night time active and usually only in the dark although they are known to become more active just before dark once they are use to you.

They will change from dark to light and back and usually are bright green while sleeping. Turning dark is fine and I have one now dark and one bright as can be and its midnight.
Like I stated, let the new frog relax, get comfortable and become trusting.

Don't handle unless needed or for inspection. Change water daily, mist with treated water twice daily to keep humidity up, and make sure there are places to climb and feel hidden such as on big leaves.

I have a snake plant that mine always sleep on and usually hide on the back side to stay are out of view.


Feel free to ask more questions too.
Good luck and ask when you have questions.