I'm not sure I've seen any perennial kinds here that were a really good, decisive purple.

I saw some with pretty purple leaves at lowes here in Arkansas, but the kind that i grow have the plain green leaves.

I have Summer Storm and it definitely has dark leaves. I saw it for the first time when it was in a rather shaded part of the nursery and the leaves were green. I decided I didn't need another green hibiscus and passed it up. Later I learned it needed sun for the dark leaves. The large pink flowers really show against the dark leaves.