I started to appreciate and love this understated Pseuderanthemum andersonii (synonym: P. graciflorum, P. graciliflorum) from the Acanthaceae Family in recent years. The common names range from Blue Twilight, Blue Crossandra to Florida Twilight.
When it is not flowering, it is not an eye-catching plant with its uninteresting green leaves. But when it does, the bluish-purple flowers do make me sit up. A link is attached below: