I've pasted in a form for you to fill out so I can comb through your husbandry and make sure all is well there.
I'll also note that it would be most helpful to get pics of the entire set up, including the lights and how your chameleon looks.
From this photo alone, and I really do hate to be the bearer of bad news as you clearly made a very pretty looking environment here, but a 2x2x4 is the minimum amount of space needed for a chameleon. You will have to purchase a larger enclosure before you know it. They are very active animals, and they grow like weeds! Fake moss (I think?) on those vines is also not recommended as we don't want them to ingest any of it.
In regards to your concern, being darker in color after purchasing them is pretty common. I didn't see much green in my first few weeks of having my guy around.
They're often scared of the new environment, and it shows with those drab colors.
Your little friend might feel a bit more secure sooner with more coverage in the middle near the top, and horizontal branches to climb and perch upon to hide behind said coverage.
Chameleon Info:
- Your Chameleon - The species, sex, and age of your chameleon. How long has it been in your care?
- Handling - How often do you handle your chameleon?
- Feeding - What are you feeding your cham? What amount? What is the schedule? How are you gut-loading your feeders?
- Supplements - What brand and type of calcium and vitamin products are you dusting your feeders with and what is the schedule?
- Watering - What kind of watering technique do you use? How often and how long to you mist? Do you see your chameleon drinking?
- Fecal Description - Briefly note colors and consistency from recent droppings. Has this chameleon ever been tested for parasites?
- History - Any previous information about your cham that might be useful to others when trying to help you.
Cage Info:
- Cage Type - Describe your cage (Glass, Screen, Combo?) What are the dimensions?
- Lighting - What brand, model, and types of lighting are you using? What is your daily lighting schedule?
- Temperature - What temp range have you created (cage floor to basking spot)? Lowest overnight temp? How do you measure these temps?
- Humidity - What are your humidity levels? How are you creating and maintaining these levels? What do you use to measure humidity?
- Plants - Are you using live plants? If so, what kind?
- Placement - Where is your cage located? Is it near any fans, air vents, or high traffic areas? At what height is the top of the cage relative to your room floor?
- Location - Where are you geographically located?
Current Problem - The current problem you are concerned about.