My recommendation :

Black painted grand prix.

if you need to buy dye for a 1 off job, it wont be cheap. Proper flower dye is not cheap !

If you get it from Holland, you can guarantee it has been drunk up correctly, and they have used roses that are laid dry for 24 hours immediately after cutting, to drink up the dye properly. You cannot use just any growers, and guarantee to get the right colour or product.