Well, I think the experts (one of which I am not) would say that it is best to breed lavender roosters to black hens because the offspring seem to get more of their type from their mother; however, since you already have a black roo that appears to be pretty nice stock, i would say breed him to your lavender hens and see what you get. After all, it seems that you would get some improvement from the cross and you already have the rooster. You just may have more culls. Ok that is just my honest opinion. Maybe one of the experts on her will chime in.