I like to grow flowers from seed. And I like the color blue.
It's easy to find flowers that are white, yellow, orange, red, purple/violet. But it's rare to find a blue flower.
The flowers for the crop, flax, are blue. Bellflowers (Campanula Persicifolia) are sometimes blue. As are Astors and Balloon flowers.
When I see a packet of seeds with a blue flower on the cover, I buy it. You can see some of the seed packets I've bought here.