What is a unique climbing vine for a partial shade trellis? Zone 4/5, something unique.?

I'm building a 7'x5x trellis for my wife that will go over the stairs to our fire pit. There is a large oak tree which shades the area until about noon or so. She likes purple (Especially deep colors) or anything unique. We are in northern Iowa and some places call us zone 4, some call us zone 5. Would like some ideas of climbing vines to plant for the trellis.