Batman isn't just the world's greatest detective and an unstoppable fighter — he's also the only person who's ever created a blue rose. Scientists have been trying to create them in the real world for decades, always without success.
Why can't science duplicate Batman's accomplishment? Turns out genetics is unable to color a rose blue — but chemistry might succeed where genetics has failed.
If you've ever been given blue roses, you have actually been given a white rose dipped in blue dye. Since people have first started breeding roses, they've been trying to come up with a blue rose with no success. Blue roses are so impossible that they've played a key part in some major literary works. In The Glass Menagerie blue roses share space with a glass unicorn as symbols of rare beauty not fit for this rough world. In DC comics, they serve as a reminder for how badass Batman and his valet, Alfred, are. Bruce Wayne gives a Pennyworth Blue to a date to impress her. (She likes it a little better when he uses his ski pole to take down the helicopter of a paparazzo, but the rose was a nice touch.) A rich cultural history has been built up about an imaginary flower that no one can grow.
Which isn't to say people haven't tried. The people who have come closest are the Suntory company in Japan. They inserted a gene that produced the purple-blue color from pansies into roses, and grew them into the Applause. (All specially-bred roses are given names by their creators.) The Applause was an expensive and celebrated rose. It was also what can only be described as not blue. At best it was a lilac shade.
Since straight-up gene switching hasn't been able to accomplish this feat, scientists are looking to chemistry instead. Specifically they're looking to anthocyanins: special pigments that change color with the pH value around them. Anthocyanins are present in cabbage leaves, which is why people can use them as make-shift litmus paper. What color they look like will depend mostly on their electrons. When anthocyanins get attached to bases, characterized by a negatively charged oxygen and hydrogen group, their electrons are fairly free. They move widely, and can absorb the wide wavelengths of red light. That leaves blue light free to bounce back to the eyes of the onlooker, making the flowers look blue. (Acids cause anthocyanins to keep their electrons on a tight leash, and only allow them to absorb blue light, making the flowers red.)
Flowers can blue up using several tactics, including teaming up the anthocyanins chromopheres with a highly positive metal ion, or by stacking them between what are called aromatic groups. Aromatic groups are amino acids that absorb UV light and shift the light going into the plant, consequently shifting the light going out. We see these techniques in famous blue flowers like blue dayflowers and cornflowers. But the best way for a plant to take on a beautiful deep blue shade is to increase the pH value in its flowers to basic levels. This doesn't just produce blue flowers, but color-changing flowers. Morning glories, when they're curled up at night, are a purple-red. When they unfurl during the day, their pH increases to about a 7.7, changing them into beautiful dark blue.
Since it doesn't look like genetics alone are going to work, it may take a full-scale overhaul of the rose to make it the blue that we want. First there would be some genetic tinkering to get anthocyanins produced inside roses. Then it's time to increase the metal ions that a blue can take up. And, finally, a botanist extraordinaire would have to raise the flower's pH up to basic levels, possibly causing it to open and close with sunlight. And all without creating a steel-lined, solar-powered base-spitting death flower. It very well might take someone on the Bat-squad to do it.