One really good combination that I've noticed in the last few weeks has been right around the birdbath as viewed from the conservatory. (I really must try and get a photo of it if the sun ever shines again.) There is a group of 3 blue flowering Caryopteris bushes (you can see them right in front of the photo, just still small and not in bloom yet), then a Russian sage and finally a Buddleia in pink.
Somehow they all work really well together for autumn color. One of my goals has been to try and create a garden that has something of interest at all seasons and I'm glad when it works out.
Linda in Austria - one of the Chelsea Tour group!!