1998 Red Penny ?

Heat treatment? When I was a kid in shop class we'd take a torch to pennies and turn them all sorts of colours, including yellow believe it or not. As they cool they eventually they revert back to some sort of a brown, red, or coppery colour, but never back to it's original shade. We always got a kck out of watching some poor sap come along and try to pick it off the table before it cooled completely and watch him sing and dance as he dropped it again mighty quick. Seems cruel now but it was funny as heck to a bunch of 12-year olds.

No, the torches we used wouldn't heat it up to the melting temperature of the copper, they were only hot enough to melt the lead solder we were using. Still a few hundred degrees, but not enough to really physically damage the coins. As for your penny, if it wasn't heat-treated, maybe it came into contact with some enviromental agent at some time in its past? Environmental damage can produce a variety of colours -- browns, blacks, "rainbow toning", and of course that lovely green verdigris we know so well, just to name a few. And now you've shown us a red one. It might be cool to collect a set of all the different coloured pennies you find and see how many there are!