The blue orpington is anything but blue! In actuality there are 3 color strains. They can be shades of silver, black, or splash. The rooster is a deep rich silver gray with black saddle back and head predominantly. The splash is a dirt white with splashes of black in its feathering. Black is black with a mild irrodecent sheen to it. You are exploring new territory mixing lavender with the roosters predominant and inheritant color genes. I can almost bet that a good percentage of the offspring will be black. The rest is a real guess. JMO.