... I don't think so, but I don't know enough about genetical engineering and biology to know.

[He knows a little bit about botany, since he has plants in his apartment, but he's never cultivated roses himself, or tried to change their colors.]

Hydrangea can turn naturally blue depending on the soil they are in, but I don't remember why exactly. Something to do with aluminum.

[But of course, trust Wei Ying to find water anywhere.]

Hm. They probably have a stream of some sort for irrigation.