The first generation cross of Buff Orpington and Lavender Wyandotte will give black chickens, with large amounts of gold or silver leakage. They will probably have rose combs like the Wyandotte parent.
If you work with them for several generations, you can eventually have Lavender Orpingtons that trace back to that original cross. It will definitely take some work-- I would estimate a bare minimum of 3 generations if you hatch large numbers of chicks each year and make very good choice of which ones to breed for the next generation. More realistically, I would expect something like 5-8 generations to have reasonable birds with Lavender feathering and correct Orpington breed traits, that reliably produce offspring like themselves (because you don't want to sell chicks that grow up to have the wrong traits, and then have unhappy buyers.)
