Wow! Those are gorgeous planting beds. And your treatment of them looks great. It's hard to really fathom how special great piles of granite are until one has lived in a place like Victoria, TX where the ground is flat and almost level for 100 miles in every direction, and furrowed land stretches out to the horizon for mile after mile along the highway.
IMO, Pinks and purples combine marvelously. Pink is the color roses do best, so it's a good choice..
It sounds like the goal is to use soft pastels, mostly. I have a few beds where I've done the same and I find some deep purple really brings them to life. Punchy dark purples would pop against those granite rocks. Purples also might work to tie together warm colored areas and pink colored areas. The buddleia certainly gets the purple thing going. Not sure if you've considered monarda - perhaps it is too leggy or too prone to mildew. But I have found it to be pretty carefree when established.
Purple Rooster might work. I've grown
Violet Queen both in New Jersey and here in AZ and am much enamored of it when it is in bloom. It could look really good with lavender/pink echinacea. It also looks good with salvia May Night. Both are low maintenance plants, in my experience. Of course, phlox can look good with these plants, although hesperus probably fills that niche.
I am tempted to recommend miniature roses as a possibility for near the edge. Cupcake grew well for me in NJ without much care. In good conditions it produces lots of neat little pink flowers over a long bloom period. China Doll, a polyantha, does the same. If white roses are admitted, I am very fond of Gourmet Popcorn for its vigor, good health, and generosity of bloom. I've also been pleased with the miniature rose Water Lily which has been in bloom continuously since May here.
It's a fun project in a great space. I've been enjoying all the photos and the chance to think about it. Can't wait to see how it turns out!
