When searching for the best piece of meat at the deli, I always steer clear of any discoloration. Sometimes, cuts of beef can have areas of a silver, almost iridescent color. It can also be a shiny green color. I've always assumed that those were spoiled, but it turns out that shiny tint has nothing to do with the quality of the meat.

The meat we buy is made up of all different compounds like iron and fat. When light hits them, it can split the colors and cause a rainbow effect. While the meat is still completely safe, it doesn't look very good. You can try to keep your raw meat away from bright lights to minimize this effect.

This same discoloration process can happen to deli meats as well. That roast beef sitting in your fridge may turn a little gray or green. Because deli meats are cured, their chemical structures are changed. After this happens, they're more likely to change color after coming into contact with oxygen or light. Just like with any meat, this color change alone does not indicate spoilage. Check for other changes in smell or a slimy feel, and only throw it away if you notice another change.