I was given this plant as a heel cutting last October. It has changing coloured flowers. My partner and I call it the 'traffic light' plant, but we don't know what it really is. Started flowering last May.
(http://i288.photobucket.com/albums/ll169/julia_swest/whatplant.jpg)
bistort?
Persicaria vacciniifolia.
Thanks froglegs, I think it could well be one of the persicarias.