While it is not reccomended I have done it and so have a few others.First generation you will get blacks and blues.All will be split for lav.The problem comes if you breed the blue/lav splits.You will not know which birds are splits in the second generation.If it is all you have to work with and are trying for lav then save only the black/lav splits to breed from.Prob a dumb question but if I breed a blue roo over a lavender hen what will the offspring be?