I remember as a kid all of the Rainbow trout had pink flesh. Some years later only a few would be pink, don't know if it is true but we were told the pinks were natural and the whites were stocked.
Actually stocked trout will eventually get the "pink" flesh color once they get enough carotene in their diet from crustaceans (like zooplankton) and things that eat crustaceans. Some hatcheries are even adding astaxanthin to their feeds to enhance colors of their fish, not just for the food market.
