The only natural strains that are truly yellow based are the Xingu wilds posted by Nandi. With the Belo Monte dam being built the entire Xingu fishery will be affected and that bloodline may be lost. Perhaps if someone would select breed and cross back the yellowest individuals of the Xingu there could be a way to create a bright yellow strain with red eyes all without color or hormone enhancement.
The trick would be finding the stock to begin with...I've never seen Xingu wilds available on lists