...I don't know if recessive white can be used to lighten anything. It was my understanding that is is sort of an on/off-type thing - either you have two copies of the recessive gene and you are white or you have one copy and are a normal-colored carrier. ...
That's the way I understand it, too - Recessive white is like a primer coat on a car's paint job... you can't see it through the dominant color. But put two coats of that on there with no real color and - boop - there it is! So we know Mr Black carries a recessive white... I'll have to do some trapnesting to isolate which hen.