I used to gaze out the window at this time of year and see a yard full of several different shades of purple, with no other color. Only height, width, and season were really considered in any planning attempt. Although not yet adept at color planning, at least now colors are considered when deciding where to place the latest acquisition.
This spring I was able to see some results of my color strategy (or at least of my thinking about color). Firey Red Emperor tulips bloomed along side blue muscari at the same time. The blue sets off the red tulips more so than if red tulips were stuck by themselves. Imagine that.
Another color consideration was given to the Salome daffodils. Notice how they start out with lemon yellow cups, and a week later turn to peachy pink. These photos are of the same blossom.
Of course, sometimes we imagine great color combinations only to find that blooms come out at different times, or that (like the daffodils) change color over time, or that there are different shades of the same color. I planted a 'red' phlox once only to find that it was more mixed with magenta: in the purple family. (oops, wrong shade of red.) It was not attractive next to the yellow zinnias. I now pay closer attention to descriptions of 'carmine red' versus 'scarlet red.'
Blooming: California poppies, poet & salome daffodils, dogwood, viburnum, azaleas, muscari, coreopsis, ajuga