dulcie2003,
I don't know much about crepe myrtles (my zone is way colder than yours) but I do know that reds (the pix I googled show dynamite as a really vibrant lucious red) can be somewhat difficult to color match.

I would go with small dark green shrubs and white annuals under/or around/or near the tree. (Will gardenias grow there? - if so that would be a good possibility - a 2 for 1 deal).

I would then try to echo the red somewhere else in the yard (maybe pots on the porch) where a perfect match doesn't matter as much.

The red crepe myrtle and the echoing reds should really pop well against your neutral house background and give it some punch, and still look very elegant.

If the crepe myrtles have and off season (no flowers) you could change out the annuals or add a few perennials in another color, or soften down the red to a pink shade which would also look great with your house color.