I have been looking for these pink or purple Congea griffithiana (Common Name: Pink Sandpaper Vine, Pink Shower Orchid) for the longest time. Finally I found it and planted it in the Indian Garden. However, I don't think it is as fast growing as the white-flower Congea. Even the leaves feel different and are more tough, unlike the soft velvety Congea tomentosa.
On the other side of Chinese Garden, I planted 3 different coloured cultivars of the Hibiscus moscheutus (Common Name: Swamp Rose Mallow, Rose Mallow). They were flowering profusely recently although it is not in flower currently. The good thing is, this species is found in wetlands and riverine systems, so it can be planted in a bog garden.