Posted: 13/10/2013 at 17:32
As puncdoc says, sometimes roses change colour a bit with the seasons. Sometimes one shoot changes colour and the rest of the plant stays the same. This is known as a sport and is one way of getting a new variety.
If you bought the rose from a reputable dealer and you have checked that the rose you think is Twice in a Blue Moon looks the same as photos of it on websites then it may just be having a little autumn moment.
Wait until next year and, if it is still pink all over, I'd take it back, if you can.