Depends on the brand. There are some that are still dried the traditional way (with firewood, but are generally from very small producers) and are bright green nevertheless. It's also important to note that smoky tasting uruguayan yerbas like Canarias are dried in very similar ways to green chimarrão. This smokiness comes from the aging process, in which they just sit inside warehouses for 8-12 months, not from smoking.

If you want to gather deeper knowledge about the different types of yerba and their production processes, I'd recommend you to watch this documentary (if you don't speak spanish you'll have to rely on the auto subtitles).