I don't know exactly what's available in Denver, but I had that barberry in a bed with grasses (get one that turns reddish or coppery in the fall) and several sedums, including the autumn-blooming sedums. I also had liatris in for summer bloom. They all got about 1/2 day of sun (AM) so I'm thinking they would work for you, too. It was stunning and very low maintenance (just be sure to pick a grass that doesn't spread, just clumps).

About 3 years ago, I planted three barberry bushes on the east end of my house. I planted an evergreen holly bush on either side (one on each end of the bed). Then I planted clumps of verigated monkey grass along the front of the bed. This is a very low maintenance bed too. I hardly have to do anything to it and have never had to do the first thing to the barberry bushes. I have had sooooo many compliments on that bed. I am very proud of it. It's right beside my driveway so everyone sees it. The colors go so well together. Good luck!