Purple Coneflower (Echinacea purpurea) used to be purple. You can still buy the purple-flowered version of this perennial (actually more of a pink, at least to my eye), but purple is only the beginning. Consider passionate hues such as raspberry pink and florescent orange. On the other hand, perhaps you’d prefer delicate pinks, or even an innocent snowy white. A related species, E. paradoxa, below, is a pure lemon yellow.