Answer:
Black
Explanation:
Why do you call that flower a "red" rose? Could it be because it appears red in a typical 'wideband' solar or household light? That must mean that when the light of many colors shines on it, the rose absorbs everything except red, and red is the only light left to bounce off of it toward your eyes. If that's the case, and you illuminate it with the light of any single color other than red, then the rose will absorb that light and appear black.
