Right now, thousands of elderly steaks are languishing in the backs of freezers, waiting patiently for their day on the grill. Hidden behind Celeste pizzas, forgotten by their owners, these once-healthy meat-slabs are slowly turning an unappetizing greenish-white, via the process commonly known as freezer-burn.
Generally, foodstuffs fall victim to freezer-burn when they haven't been sealed properly. This lets valuable water molecules escape into the colder parts of the freezer. These molecules tend to stick to the outside of the container and form an unappetizing layer of ice crystals. Once the water molecules have migrated away from your food, your dinner becomes dehydrated and discolored.
This slow deterioration can be avoided with the right plastic container, but freezer burn is ultimately inevitable. If you leave something in there long enough, it will get dried out, no matter how tightly you've vacuum-sealed it.
That said, you should never judge a rack of ribs by its off-putting discolorations. Freezer-burned foods are totally edible, in the sense that you can eat them without dying. Taste- and texture-wise, food that's been freezer-burned leaves much to be desired.