Oxygen is your friend. The meats I buy come in plastic packages, but when I open them I either age them in the open air or store them in mostly-glass containers (the lids are plastic and metal). Plastic is anaerobic, so I try to avoid using it, but it's not easy.
If your red meat turns light brown (it looks like the red is drained out of it, like it has anemia) instead of dark reddish-brown, then I believe it means that surface of the meat aged anaerobically, and it won't taste as good as aerobically-aged meat. It's not likely unsafe unless stored anaerobically for long periods, which risks developing lethal anaerobic bacteria like clostridium botulinum (which increasingly are killing Inuit who have been storing more of their raw fermented meats in sealed plastic). Aerobic bacteria are the friendly little guys that make the Inuit feel "high" when they eat high meat.
I'm not sure why meat on top of meat has such an anaerobic effect. Lex, do you know?
Man, all this talk of aged meat is making me wish I had a meat locker to hang meats in.