I was never fond of Rose of Sharon, but all that changed when I visited the Cherokee Botanical Garden and Nature Trail in Cherokee, NC about 20 years ago.  It was the most beautiful botanical garden I had ever been in, and nothing has topped it for me since.  It's located beside the Oconaluftee Indian Village, and if you're ever in the vicinity, you should drop by.  I saw two Rose of Sharons that day that completely changed my mind about them:  one was "Blue Bird" shown here, and the other was "Diana," a pure white-flowered variety.  After that day, I was on a mission to find both for my own garden, and I didn't stop until I did.   "Blue Bird" is the most beautiful Rose of Sharon in existence, if you ask me, and whenever anyone sees it in my garden, they agree.  The color is azure blue with a splash of lavender mixed in, and the center is deep garnet.   It grows to about eight feet in my garden (maybe up to 12 feet in someone else's) and is completely covered in these beautiful blue blossoms in mid-summer.   It likes full sun/light shade and grows in Zones 5-9.

This is the pure white Rose of Sharon
that changed my mind, along with "Blue Bird," about Rose of Sharon forever. 
There is no center color - just a clean, crisp, pure white all over.  It's just lovely.