How can i get a white rose to turn two colors at the same time using food dye?

reall need help, i want to dye white roses two color in memory of my brother that past away . he loved black and yellow so i wanted to make him a flower bouquet for his 1 year anniversary. please help i know those roses cost alot and im wiling to pay but there are no florist in the i.e that want to get my order ,so i want to do it on my own. thanks :)