Kristin, the plants we have are green on the bottom and purple on the top. If you want to get rid of them, make sure you pull them out by the root. I'm not kidding when I say they can be very invasive. They started taking over our birds of paradise.
But they are so pretty and I love them, but if I get lazy, phew, I cause myself so much extra work. They definitely need to be thinned out on a regular basis.
I do know that they are definitely hardy because my family has always had them in upstate Pennsylvania which is more similar to the weather there in Canada than it is here in Florida.