When beef is first cut, it is dark reddish purple in colour, but within minutes its surface quickly turns to a bright red in the presence of oxygen. However, if the oxygen can't get through the packaging material, the meat can remain dark. For the same reason, it is natural for the inside of a package of ground beef to be dark while the outside is bright red. If beef has been well aged, it can also be slightly darker in colour. Variations in colour can be due to many factors including the type of packaging, and therefore are not important indicators of quality.
Many consumers mistakenly believe that fresh beef can be dyed to give it a bright red colour.
Rest assured, government regulations prohibit the use of any colouring, additives or preservatives in fresh beef. Ask about Aging Beef, like fine wine, improves with age. The term aging simply means the length of time beef cuts are stored under controlled conditions of temperature and humidity before they are packaged for the meat counter. Aging allows naturally occurring enzymes within the meat to slowly break down some of the connective tissues that contribute to toughness. Aging times vary considerably from 3 - 21 days.