Would this be like a Palomino? One needs a chestnut horse and a Cremello which acts as the diluting gene on the Cheatnut to give that yellow body with white mane and tail Palomino.Read the first sentence. I wasn’t making it up. Hattie is a lovely black chicken with a very special addition.
https://poultrykeeper.com/poultry-breeding/the-lavender-gene/
But if you breed two palomino your have a 25% chance of a chestnut and a 25% chance of a Cremello.
If you bred two greys would one get a lavender and a black ?????