I detect these at the beach all the time. The term Red has to do with the color variants of Cents. The chart I have provided will help you see and understand. It's like the toning of copper. Not that it is actually red. I want to share this webpage with you - http://coins.about.com/od/coingrading/tp/Grading-The-Color-Of-Copper-Coins.htm
Also..I believe that your Cent and the ones that I dig up at the beach might have to do with 2 factors. First, the sand which roughens the surface after years of tossing around will act almost as a sandblasting effect. Second, the heat of the sun will bake the copper that Dark Red color. Hence Environmental Damage These are just my theories
With this being said , I believe I have one red cent sitting at home . I will post pictures when I get home today. Thanks paddy
That's an environmental damage and/or altered surfaces color. The coin has been in a corrosive environment of some sort.