Okay, you may think this is one of those threads asking if blue roses are real already but I assure you it's not. It's more of a "What If" thread.
What if someone somewhere successfully bred a blue rose. What class do you want it to be? Any scent you have in mind? Foliage and habit? What shade of blue would you like it to be? Ocean Blue? Sky Blue? Navy Blue? Cerulean? For me, I'd like it to be this kind of blue (and yes, this photo was manipulated):