If you think buying a "green" car is as easy as picking the paint color, we've got news for you--there are different types of green and many different car choices. Are you trying to reduce smog and its attendant health risks, or are greenhouse gases and global climate change your biggest concern? And those aren't exclusive concerns, either. Amongst the types of cars you can choose, there are hybrids, PZEVs, SULEVs, flex fuel vehicles, natural gas vehicles, and even diesels. We also take a look at future technologies that are in heavy development and could the be cars of the future.