When it comes to candy gone ‘bad’ is normal to take one look and say ‘ugh, NO THANK YOU’. Sure, it’s not appetizing to look at, and you might rather lick your shoe than take a bite, but if you DID eat it, would it be safe? The short answer is…. YES.
But I think it’s still gross. Ew….
WHY IT TURNS GRAY…
There’s nothing quite like opening a much-anticipated box of chocolates only to find discolored, slightly gray candy. When chocolate turns gray like that, one of two things could be the culprit: sugar bloom or fat bloom.
Sugar bloom is normally caused by surface moisture. The moisture causes the sugar in the chocolate to dissolve. Once the moisture evaporates, sugar crystals remain on the surface. If this process is repeated, the surface can become sticky and even more discolored. Although sugar bloom is most often the result of overly humid storage, it can happen when the chocolate has been stored at a relatively cool temperature and is then moved too quickly into much warmer surroundings. When this happens, the chocolate sweats, producing surface moisture.
Fat bloom is similar to sugar bloom, except that it is fat or cocoa butter that is separating from the chocolate and depositing itself on the outside of the candy. As with sugar bloom, the most common causes of fat bloom are quick temperature changes and overly-warm storage.
Although it might look a little less appetizing than a lustrous, rich chocolatey-brown piece of candy, chocolate that has suffered bloom is still okay to eat. You may find the texture of sugar-bloomed chocolate to be a bit grainy on the outside, but it should still taste good. To prevent this from happening to your chocolate, simply use proper storage methods.
Whether it is white chocolate, baking chocolate, milk chocolate or some kind of chocolate confection, proper storage is key. Since it can easily absorb flavors from food or other products situated nearby, chocolate should be tightly wrapped and stored away from pungent odors. The ideal temperature for storage is somewhere between 65 and 68 degrees Fahrenheit (18 to 20 C), with no more than 50 percent to 55 percent relative humidity. If stored properly, you can expect milk chocolate and white chocolate to be good for up to six months. Other types of chocolate can have an even longer shelf life.
Via How Stuff Works