Welcome to the wonderful world of protective coloration, Louie.
TLTFs can range anywhere from the bright, vibrant lime-green... to a muted, light brown... to even a greyish brown with speckles.
It entirely depends on their environment: plants, temp., humidity, etc. Even time of day. The same frog could be three different colors three different times you look at him.
At night, when they are most active, I've seen them darken to almost a choclatey brown... only to be a speckled greeny-brown in the morning. It's all part of their natural behavior. The wax they secrete also adds to the color changing fun by darkening slightly when it dries.
For a weirder time, you should see them in breeding time. If you cycle them right (dry them out, and then stick them in a rain chamber come spring)... big females in breeding condition will even turn a beautiful blue-green... almost turqoise. It's a trip.
As a first frog, it's not the most spectacular... but they certainly are hardy frogs. I wish you all the luck. In time (couple of months), they'll even perch on your finger for a few minutes at a time. Just make sure to wash your hands very, very well before handling them.
If you want some more fun in a couple months, once you have husbandry down pat... go grab a little 10 gallon tank, and a Pacman frog. Those guys, even though they just sit there, are an absolute blast.