Dwarf crepe myrtle. You can get them in magenta flowering, they bloom when not as many other flowering plants are blooming. They come in various sizes too, from bitty shrubs to much larger shrubs but way shorter than trees.
Vitex is another shrub to consider. It can become tree height, but just cutting it back early in spring will help keep it in bounds. Nice blue flowers.
Deer are not fond of viburnum either. They don't flower in your desired color scheme, but something to consider.
Butterfly bush are my last suggestion. You can get them in a reddish magenta color, and of course in purple, and there are yellow ones too. The yellow can get large, just prune back again, in the spring.

Happy gardening!I hope you can find something that suits your needs. It sounds like a beautiful spot!!

GGG

Good suggestions.

I have some dwarf crepe myrtle that are loved by Japanese Beetles, so I'd have to be sure to pick off the beetles everyday when they're about. The beetles don't bother my large crepe myrtles, but they love the shrubs for some reason.

I have a vitex as the center attraction in my butterfly garden, so that would provide a relationship between the gardens.

I told my husband over dinner that I'd probably end up with a butterfly bush -- I already have Pink Delight and Adonis Blue in the garden. The pink is to the left of the monarda and the blue is to the right of the coneflowers, separated by pale yellow coneflowers 'Sunrise', coreopsis 'Creme Brulee' and pale yellow snapdragons.

I'm also wondering about using caryopteris. Those do well here and bloom in the late summer.

How about a spirea -- this one looks interesting and dramatic. though it gets a bit taller than 3' . . .

Here is a link that might be useful: Spiraea Golden Sunrise

Spirea is an excellent suggestion! I have magic carpet and I love it.
Caryopteris is also beautiful. I am just cutting mine back a bit. I find an early pruning helps keep it a bit shorter during the season. They can get leggy in the South.

GGG

I like GGG's suggestions. I'm not particularly fond of buddleia, as most grow to gangly proportions and require lots of cutting back to keep in good shape. Personally, I would go with a viburnum. There are so many to choose from, both deciduous and evergreen, even though they don't bloom in your colour choices.

Another option would be a broom. There are yellow and reddish cultivars and they are striking plants. I have a reddish one that is covered in flowers at the moment, providing a great focal point. You could also grow a clematis to climb the broom and provide an extended season of bloom.

Yet another alternative would be an witch hazel. This would bloom in Winter and there are cultivars with flowers from yellow to orange variations.

Eduarda

There are alot of very pretty cultivars of weigelia also - from deep maroon leaves to varigated yellow/green and everything inbetween. You will have the beautiful bloom mid/late spring and then the pretty leaves afterwards. They can handle pretty severe pruning to keep in your desired shape and area........

Lynne

Here is a link that might be useful: Weigelia facts

I have broom in other parts of the garden and my soil is just too rich for those. Mine are the rose color. They've done fine, but they could be more impressive. I fell in love with broom on a trip to Provence several years ago.

The spireas are a great suggestion! I've decided to get 'Neon Splash'. I have several varieties of spirea (Goldmound, Magic Carpet, Limemound) in the garden, so this will work and provide the bloom and foliage color that I want.

Neon Flash has the colors of the monarda and the coneflowers in the bloom and the foliage will turn to burgundy in autumn. It's the perfect size, so I'll group at least 3 together. (My friend at the nursery says this is replacing Anthony Waterer and he has Neon Flash that are already 15" high.)

THANKS!

Here is a link that might be useful: for picture only

Lynne -- we cross-posted at the same time. I considered weigelia, but I have had problems with the deer picking those blooms. I had several at my previous house near Jordan Lake.

Thanks

How about grasses? Some of them bloom with pink plumes or have reddish blades. The spirea will be pretty as well, very splashy color!

I considered grasses -- I have so many already in other parts of the garden. That's part of my problem with coming up with plants. I have such a large garden, there are many, many types of plants already in use and I'm looking to 'branch out' in this spot! :-)

Thanks!