Blue roses were traditionally created by dyeing white roses, since roses lack a gene to produce delphinidin, the primary plant pigment that produces true blue flowers. So-called “blue roses” have been bred by conventional hybridization methods, but the results, such as “Blue Moon” are more accurately described as lilac in color. Blue rose was created using genetic engineering. The delphinidin gene was cloned from the petunia and inserted into a mauve-blend rose. However the rose was more dark burgundy than true blue. That is why most florist would still prefer to use flower colour dye or food dye to create a blue rose.
Blue rose signified hope against unattainable love. There are various versions of this story that can be found online.