Mario,
Check out some of the websites with the major breeders, mine included, but go to
www.Kingsnake.com chameleons, and go through the sponsors websites at top. Read all the husbandry pages. You have much to learn. Even if it was a gift, and if you paid for it then shame on you, but taking on ownership of a 3 week old chameleon is not a wise move. Its done, but learn from your current experiences, and websites, and don't do it again.
Color is a function of size. It won't show color as Jeremy said (sorry Jeremy. Let the reader know that you only live 10 miles form me, and we've met, and I know you mean well. You're just wrong about showing color at a few weeks.) It will need to be at least 5" total, and likely more, before it shows color. You may be able to sex it sooner, but it will be by pattern, and not color. Just be patient, as you can't change it anyway (if it was human and living in San Francisco, maybe). On top of it all, your animal is claimed to be Ambanja, which is west-coast Madagascar. If it is an east coast animal (Tamatave of Sambava, ie.), or a locale-cross, it will take longer to color-up than a typical west coast animal (Nosy Be and Ambilobe included). You really have an obligation to the animal to educate yourself, which you had not yet done judging by your first post. Its your animal, and if it has an early demise, its your loss. Check those websites.
And Wendy. Congrats on your new task !! Take care.