Although I myself am not a citizen yet, I have started a RWB garden. It's also not very large, and has some natives.
There are native lobelias in red, blue and the harder to find white. Those are the real native plants in there.
Ipheion bulbs
white reblooming iris
siberian iris "Baby Sister"
red, white and red/white striped amaryllis which, if given good drainage and 1/2 day shade is hardy here
white campion
pratia which is a groundcover with little blue flowers
red fruit sage which blooms very, very late in the season for great color
white dwarf asters
dwarf blue balloon flowers

GGG

Congratulations, Barbara. A favorite blue native is phlox divaricata - spring bloomer. Also thalictrum kusianum (sp?). Both are shade plants, so won't work if you're planning a full-sun garden. For white, I love Bridal Veil astilbe - another shade plant. I'm going to have your RWB garden down by the creek bed. Except for lobeila I can't think of a red bloom that does well in shade, so I guess you better stick to sun. Again, congratulations.

How about Blue Star Lobelia? I planted some last year in a sunny location, and they were beautiful.

Amsonia, many cultivars, and they have a lovely blue color. Beautiful, glowing yellow fall foliage.
For early season red there is Aquilegia Canadensis and it's dwarf cultivar "little lanterns". They do have yellow inside, so are not pure red...but lovely! They re-seed nicely.
Both are native.

GGG

Congratulations Barabara!

Everyone has great suggestions. The few I have to add are mostly non-native, but would give you something blooming year-round.

For the blues: Baptsia, Spanish Bluebells, Hydrangea (mine are in shade but I've seen them in full sun), Stokesia 'Blue Danube', and some blue pansies or violas during the winter.
White: Calla Lilies, Brugmansia 'Suaveolens White' or 'Candida Double White', white Liatris, butterfly ginger, white helleborus, and white daffodils.
Red: I don't have much red but I have a gorgeous red daylily called 'Red Rogue' that looks like red velvet when it's blooming...has a small yellow throat so it isn't solid red.

Good luck and that's a great idea for a theme bed!

thanks to you all. i will look closely at the suggestions and let you know what i decide on!

Congratulations, Barbara! What a fun idea. I was perusing through my native books, and found a nice woodland garden combination: Atamasco lily (Zephyranthes atamasco), Spigelia marilandica, and Phlox divaricata.

Part sun: Silene virginica has awesome red flowers

Full sun was tougher to find: Boltonia asteroides has white flowers (farmerpickle has some of this on her trade list), Stockesia laevis, and maybe Cardinal Flower or Bee Balm

You might want to try posting on the native forum, too.
Good luck. Can't wait to see pictures!
Pam

Oh yeah, I forgot to mention Coreopsis "Ruby Limerock" (I think it's a native), and white Liatris spicata for a sunny spot.

If you're interested in a piece of Spigelia marilandica, I may be able to get you a bit. I transplanted mine, so I'm hoping they all come back! It would probably be small, tho.
Pam

Barbara, I don't remember the name of one of the plants I gave you last fall - serious senior moment - but it is red, blooms in full sun to part shade, and produced blooms for me all of last summer. I think I gave you two of them - the woody perennials. Hope it helps with your new garden.

For white in the sun, how about Phlox 'David'?

Texas Star hibiscus (Hibiscus coccineus, I think) takes up some space but makes a wonderful red statement.