Are you referring to Centaurea montana (perennial) or Centaurea cyanus (annual)? The annual species can be easily grown from seed by simply throwing them where you want them to grow. Colors, besides the cornflower blue, include pink, white, and purple. I have seed if you want it.
The perennial blooms fairly early in the season but can sometimes be induced to re-flower later if cut back. The only bloom color I've seen is blue. I believe I got mine via mail order; probably from Bluestone Perennials. I have never known this plant to be invasive, but occasionally it reseeds itself.

I find the annual does best if sown from fall through about feb- it likes cool weather. This way, it ill have time to get big and flower before the heat sets in. As much as i like the perennial, i've never found the magic spot for mine- the heat seems to get it every time. There also is a deep pink version of the perennial, i believe it's c. maculata or persian cornflower. At any rate, i bought the seed at one of those racks at a big box- and it has been a very reliable perennial for me for at least 6 years. hasn't reseeded, though i wouldn't mind if it did. The leaves are different in it- looking a lot like valerian, the herb. Lovely plant.

Thanks for the offer of seeds, I have some of the annual seeds already, and I winter sowed them a few weeks ago, and put half away just in case I screwed something up, They sprouted within a week and I potted a couple dozen up and brought them in under the lights in my propagation room. They are doing well to this point. I left the other seedlings out in the cold frame to fend for themselves.
Thanks for your replies.

I have grown them for at least 10 years with huge success sowing Spring and late Summer. They are now on their own sowing themselves with wild abandon, which results in an ocean of blue and pink flowers June and July. Not invasive, easy to weed out if necessry, but generous resowers. The best part besides heavy flower display is the green they provide all Winter. My garden is full of them as we speak. The basal rosette of leaves stays about 6 inches long all winter, which gives them a headstart for faster bloom than those sown in Spring, but still good for a longer show to sow in Spring too. The seeds are so easy to harvest for sharing and saving. And the bouquets! It's a winner.