Ciao simcep, I am not sure I understand well what you say! But when you say to cross the red with black!? Look the genetic code, on the E-locus the red is (should be) EWh/EWh, that of the black is (should be) E/E.
When you cross these two you become E/EWh, the "E" is dominant over the "EWh" !!!
For as far as I know the red with the grey pluff are on the E-locus eb/eb, these with the red pluff are EWh/EWh. But I am not specialised in this color, a friend of mine is. The only way to become the red good red is (as with all) selection, selection, selection.