The film is adapted from the novella 'Rita Hayworth - The Shawshank Redemption' told in the first person by Red, who as the nickname infers, is caucasian, with red hair - a fact overlooked by the film casting people - to no detriment of the movie what ever.
The book is one of the few seriously good adaptations of King's work - it is a wonderful story of optimism, and the genuine good to be found in even the worst places.
Your friend has either misunderstood the film, or is simply teasing you - but rest assured, Red is real - well, in the novella and film anyway!