Our first house sat in the deep shade of about a dozen large trees, so I learned early that there is a wealth of plants that thrive with very little sun.
Finding shade plants with brightly colored blooms is a bit of a challenge, but one that I've had good luck with is astilbe. My pink one, pictured here, grows in the deep shade of dogwoods all day and contrasts well with the heavy-leaved hostas and the hellebores. It began blooming about the middle of May and really brightens up the dark corner by the birdbath. Astilbe can live in part sun, but they need to be watered very often, or they'll dry out. My lavender one sits about three feet away, but gets sun for several hours during the day and the leaves frequently get wilty. Last year, one of them got this nasty white fungus and died, but so far this year I've had no problems.