e.e. cummings’s tribute to his mother opens with these lines:
Is there really a variety of rose known as “blackred,” or did cummings invent the term for the poem?
I don’t know if there is a variety called blackred but no true black roses exist. Rose sold as black ones are really a dark maroon rose whose petals tend to get badly scorched by the sun.
I have a one in my yard with the name Nearly Back. when first opens, it is an extremely dark red, like very old blood. As the bloom opens to full, and ages, it lightens to about the same color as * Mr Lincoln*
Sorry, I meant to put this in.
I’ll try to find a picture of the Nearly Black too. BRB
here is an example of Nearly Black.
I once saw a blue rose.
Ofcourse, it was spray-painted blue, for a wedding, but it was still blue 
I have a blue rose that I bought in a Central Market in Austin about a year ago.
Apparently, it turned blue because they added blue food coloring to the water it was watered with, or somesuch. The leaves had a bit of a blue tint to them, but the rose itself was BLUE.
Just felt like sharing. Maybe they could do the same kind of thing and make black roses.
Poetic invention. IMHO.