What is it with the Bishops? There is a run on ecclesiastical dahlia naming. We have got the Bishop of Llandaff in two flowerbeds and the sister in law has just had Bishop of Auckland foisted on her. Could it be something to do with cassock colours? Anyway, the point of singling out black as a reoccuring theme, is to do with the slateyness and dulling down of foliage. For instance, our house is plastered and painted sugar-mouse pink. Dark colours sing against it.
Dahlias give a colour zip from now until the first frosts. Many have wonderful dark brooding foliage. The white flowered forms can be even more intense.