I have to second @Rosyrain
, any color except orange. I don't know why, orange just doesn't go with the other colors as well. It's brash and harsh.
, for purple flowers, try cleome, even though some are pink and white, purple is the predominate color - plus they reseed themselves. They grow about 4-5 feet tall, but start producing flowers at about 2-3 feet and bloom almost all summer.
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Also try Verbena - again they come in different colors, but have some really pretty purples - both dark and light. Some are perennials, some are annuals. They are a lowing growing plant, about 6 inches tall, but they spread to cover about 3-4 feet or more.
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And then there's always Clematis. They are a climbing plant with really big blossoms.
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