The Color Purple Blues

I have yet to understand why a perfectly purple flower in the world of botany, is known as a "blue" flower. But it is so. On our last drive down to St. Marks, purple/blue was the color of spring. Here is a sampling:

Blue Flag Irises were quite plentiful.

Spiderwort

Native Wisteria

Blue-eyed Grass

Thistle

Leather Flower