@La_Chica: lots of things that aren’t actually covered with green pigment are metaphorically described as “green” if they’re environmental. For instance, the Prius, a hybrid gas/electric car, is “green,” even if the actual car is blue or red.
In this case, I think the question asker is asking about environmentalism as being a “green,” or eco-friendly, religion. This isn’t as strange as it would appear, as there are many people out there who treat Environmentalism as a part of how they worship, or as something they do for spiritual reasons. (Wicca is known for its adherants trying to be kind to nature. There’s also the Gaia Hypothesis which describes a belief that the Earth regulates itself as a sentient being might, which some people feel has religious or spiritual overtones. There are even Christians who feel that God wants them to be good stewards of the Earth.)
In these cases, though, I think it is environmentalism that fits itself in as a platform for some peoples’ “green” religions/spirituality, and not necessarily that Environmentalists (who may be of any religion) practice some kind of ecological cult. Looking at it this way is, I believe, putting the cart before the horse. The only time I hear people describe environmentalism itself as a religion or cult is when they’re trying to be a troll by making people who care about the Earth look like ridiculous wackos.