Have you ever opened up a pack of bacon only to find it looking a bit too green for your liking? Green bacon seems gross and inedible, since we most commonly associate green with mold and spoiled food, but the green in bacon is no big deal.
It's called nitrite burn, and it's caused when the preservative nitrite reacts with the blood protein myoglobin, causing the red pigment in the blood to turn green.
Bacon has a distinctly awful smell when it spoils, so trust your nose and you'll know when your green bacon has actually gone bad and when it's just feelin' the (nitrite) burn.
-Via mental_floss