Choose Purple Acacia or the gorgeous purple flower showers of a Jacaranda tree.
Purple Acacia: 10-25' leaves range from dusty blue to deep maroon in color, casts sparse shade, requires little water, does best with seasonal dose of a fertilizer called chelated iron (buy here).
Jacaranda: 30-45' casts full shade, loses leaves briefly twice a year, requires moderate water, carpets the ground with purple flowers when in bloom.