A bird can hatch from a normal speckled egg and still have 2 copies of celadon, because each parent could be a carrier. To know for sure with a roo, you need to breed him a lot to hens who lay blue eggs, raise the chicks, and see what his daughters lay. Once you’ve raised dozens and dozens of his daughters, If every single one lays blue, he probably has 2 copies. I had tracked 80-100 daughters of mine, when I felt certain, I raised my prices a bit, but I still asked every customer to tell me if they lay blue, and many sent me photos of all lovely blue eggs.