Yes I'm on to the black roses, if you water them with black tinted water they grow even darkerI have purple pink and white hyacinth....and my hardy primrose came in...really nice deep purple color, but yellow centers so wouldnt work for your black and white idea..
there are black roses ...most of the black flowers you find are really an incredibly deep purple/wine

I'm thinking black lilies , black calla lilies, black hollyhock, black iris, black poppy, voodoo lily, black pennies, black bachelor buttons and more....