I did not carry blue flowers, but I put a lot of thought into it.
Have you ever heard of design master floral paints? Well, they are really wonderful for making flowers the color you like (we used them on white roses and calla lilies to make them a deep pink for a bridal shower- white calla lilies cost A LOT less than deep pink). DM paints are formulated for real flowers, look pretty natural if you’re patient spraying them (do a few coats so there’s no dripping), and come in so many colors.
I ordered mine from here http://www.crafta.com/floral-supply-floral-spray-color.html
Frankly, I love it when brides mix some white in with a blue bouquet to balance it a little but. Mrs. Tiramisu had a beautiful bouquet
but hers was a little more purple- you could do something sort of similar and use the spray if you wanted flowers which were more blue.
On the knot there is a page which features blue bouquets/flowers http://weddings.theknot.com/ODB/themes/realweddings/results.aspx?STOPREDIRECTING=1&type=3&wedding_details=Bridal+Bouquets&colors=blue&MsdVisit=1
Flowers you could use that are naturally a true blue-
Blue Hydrangea, orchids- http://www.fiftyflowers.com/product/Blue-Dendrobium-Orchids_10.htm, thistle= http://www.fiftyflowers.com/product/Blue-Metallic-Thistle-Flower_10.htm, Delphinium http://www.fiftyflowers.com/product/Light-Blue-Delphinium-Flower_10.htm, blue roses
Flowers you could enhance with color that would be pretty:
Anything white- examples: roses, calla lilies, peonies, garden roses, hyacinth http://www.fiftyflowers.com/product/Hyacinth-White-Flower_8.htm, Phlox, tulips, dahlias, mums, daisies- the possibilities are unlimited.