Snapdragons can also tolerate light shade. Begonias always can tolerate shade well in Cheyenne. There are some excellent choices for perennials in the shade . One of my favorites is Bleeding heart has fascinating flowers that live up to their name but only bloom for a few weeks. Delphinums with their tall blue spikes can tolerate a fair amount of shade.
Columbine grows well in shade but blooms best if it gets a little sun during the day.
Vinca grows in a viney fashion with glossy green leaves with a blue flower appearing in spring. When you are purchasing flowering plants for a shady place try buying the varieties with lighter colored flowers because they will show up better in the shade. In especially dark, shady places it is particularly hard to get plants to bloom. This might be a good place for perennials with interesting foliage. It has attractive wide leaves and can be found with stripes, green and bluish foliage.