Head etc color is due to sex linked gold and silver alleles.
Domi are silver and orpi are gold- this is a sex linked cross producing males that are silver (white) and females that are red/buff/lemon. It has been my experience that black/barred birds are silver- I agree with Jeffrey on this finding therefore domi is silver. Domi could be gold but I am going with the highest probability.
Crossing the two birds produces an extended black/wheaten heterozygote. This genotype will produce incomplete dominance- and in the correct genotype; males and females that leak non-black color on the anterior of the bird. Greatest in hackles. Also any melanizer found in the domi would also be heterozygous in the offspring which will lead to more non-black expressing on the anterior of the offspring.
The orpi carries a gene called dark brown that will suppress black plumage on the anterior portion of a bird; therefore the non-black head, hackles and breast. The amount of black removed depends on the genetics of the barred birds. The offspring could have a little or a lot of the black removed from their anterior end.
Tim
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Thanks Tim very helpful.I am writing it all down for the future.One more question related. On BBS Orps .... the brown supressor on black would that cause the blue orp?