Your zone may be reducing your potential pool of responses here, as is the fact that your question is probably more suitable for the Tree forum.

I like dozens of trees, but I have no idea whether they could survive in your zone. The trees people will.

KarinL

Here is a link that might be useful: Trees Forum

I thought the same thing Karin but it is half way a design question and half way a tree selection Q. The "purple foliage" is the design part.

Suggestions:

Acer ginnala
Betula nigra
Carpinus caroliniana
Cornus alternifolia
Magnolia acuminata
Magnolia kobus
Magnolia stellata
Quercus ellipsoidalis
Sambucus canadensis
Syringa reticulata 'Ivory Silk'

Dax