Leakage can be used in certain instances. If you have a great typey black pullet with just a touch of gold leakage I would pair her up with a very brassy partridge boy.
He's a very pretty boy and very typey but, he lacks the black in him. Therefore a black girl with gold leakage could help. But if the Black girl had Silver leakage I would say try her with a Grey Boy.
In other words I would never breed her to black b/c this leakage will only crop out later and worse in the boys. But, b/c you like her and feel she has type down I would use her in a way like I explained above.
Good Luck
This is such important info! Very pretty boy too! What about red on a splash. Any hope there?