DSR, you took the words right out of my mouth!! That was my first thought also! I'm thinking that maybe it's a mutated gene? It would be interesting to see if they could breed an offspring with the same coloring.
P.S. Interesting that this story turned up on Martin Luther King's birthday... a creature with two colors. If they hadn't saved it, maybe all the other lobsters would have been prejudiced toward it (hehe)