This article gives a nice background on the history of roses as a coveted flower, and then gets into the matter of a blue rose.
A blue rose is held to be about the hardest thing in the flower-growing world to attain…
It can’t be done by any chemical process, of course. Any one rose can easily be made blue, but there is no known way of treating the soil in which a bush grows so as to change the color of all its flowers, and even if there were such a way the progeny of the roses would revert to the ancestral type. The blue rose is to be obtained — if it ever is attained — by combining roses of different colors and using the most promising as parents for a newer and bluer race.
There has been a pale lavenderish-blue rose produced by a German grower, but it is not by any means a true blue.
Well, that problem vexed growers for another 100 years until a Japanese company proclaimed that after twenty years of research and three billion yen, they genetically engineered a blue rose. Well, I guess it’s sort of blue. To me it looks like a pale lavenderish-blue, not by any means a true blue.
HAVE YOU EVER SEEN A BLUE ROSE? A HORTICULTURAL PROBLEM: Many Varieties of the Queen of Flowers Created in a Century, but Blue Roses Still Elusive. (PDF)
From July 30, 1911