Hey,
i have been growing and cultivating orchids for 12 years now. Orchids from home depot and other nurseries usually sprayed with pesticides and fertilizer. So, I would not expect to put them with your chameleon. There are several species of orchids usually available at home depot, paphiopedilums, phalenopsis, catalleya, dendrobium, onciduim etc.... Catelleya, dendrobium and oncidium are more hardy and can withstand higher heat and sunlight than phalenopsis and paphiopedilums. Plus, they grow and bearing shoot much faster than phalenopsis and paphiopedilums. Taking care of them is fairly easy..... they grow on mixture of bark, charcoal, sphagnum, perlite, (NEVER GROW THEM ON SOIL...this will KILL THEM). They need porous growing material, and since it is porous.... you still need to make sure the potting material is damp but not soggy; waterlogged. They can be grown at about 50 - 70% shades, so putting them in ur chameleon cage should take care of it.
(FYI - Veiled Chameleon are monster...they will chew and munch on any edible green and flowers, so if you want to decorate ur cage with orchids, it is a really really bad idea to have a veiled chameleon in it)