The Hydrangea is the Head of the Department of Trans-Dimensional Hopping and Snatching. The halls leading up to its office are blue, painted with photo-realistic clouds.
The Hydrangea itself is a no-nonsense sort of Plant that expects a lot of its agents. It was unmoved when Meg Thorton demanded a partner, yet regarded her with a methodical, sensible demeanor. The Hydrangea may dislike annoying singing or loud noises, but it may just be that '99 Bottles of Beer' is annoying to just about anybody.
The Hydrangea is both pink and blue. In mundane hydrangea plants, this is caused by soil acidity — it's possible that the Hydrangea invokes this purposefully for cosmetic value.