They can stay green as long as they have plenty of air and it's warm enough. In habitat the roots are growing on tree trunks fully exposed to air, but wet for many months of the year, if not all 12 months.

I feel your pain…
 

I live in New Orleans, possibly near you, so I know about the difficulties of finding anything that is in a garden center that hasn't been overheated with what little natural moisture is in it to a state of moldiness. Every bag of soil or potting medium that I buy from any local big-box stores has had questionable things already living/growing in it. I have learned that anything that I'm going to be potting my orchids up in will need to be boiled – I boil my LECA for 20-30 minutes. I order my Orchiata bark from Amazon, and that has never given me any trouble, and even though all of my orchids spent the whole summer outside, they didn't bring any pests in when I brought them back in a few weeks ago. The Orchiata bark is really hard and the bugs seem to not really be interested, and the orchids in LECA got a very thorough flushing when they came in. I did a precautionary spray of Physan 20, and everything is adjusted well. I see that you found some good bark, but if you need more, and are in my area, I'll let you know where I found some reasonably-priced bark/charcoal mix that is at a mom and pop type place.