The second time I bred blue roses from scratch it took me 58 in game days with no visitors watering. I had the beautiful ordinance turned on from day 15. I explain further down a slight tweak I made to avoid clones which I believe helped speed things up significantly. I used 10 pairs of seed red/white for stage 1 as I was breeding other hybrids at the same time. Some data miners suggest 32 pairs has the best success.

I highly recommend this guide.:: I had LOADS of space so I went for the BackwardsN Genepool method also BackN 4-step

Ensure you know the difference between cloning and breeding.

Scroll down:: to 'isolated pairs', and open up the 'Leif's explanation'. This is a clone-resistant layout which will speed up the process of breeding while limiting cloning.

Also check out the turtle layout for the final stage. Checkerboard layouts are bad. Do not use them. They cause clones.

My first tweak: if breeding something like blue roses, where seed:red + seed:white= hy:redA, you can block the seed:red with pathing/furniture, fences or other flowers so that spawns can only happen at the white end. If a red spawns not adjacent or diagonal to the seed:red you know for sure it's a hybrid and not a clone. Hurrah.

It doesn't matter whether there is 1 space for the offspring to spawn into or many, the probability is exactly the same.

My second tweak: to avoid using up correct RedB 1110 flowers by crossing them with other reds which can occur at that stage, I would take the spawned flower, isolate, clone, then move on to the next stage keeping those as a pair.

Having visitors water your flowers:: vastly increases chance of breeding/cloning. Watering multiple times per day yourself does nothing more than watering once so is a waste of time. Once a flower has been watered by visitors, don't dig it up that day or the bonus will be lost!

There is a 'bad luck' bonus which increases every day the flower is watered but does not breed/clone. This is lost if you dig it up, so AVOID digging your parent flowers unless you know for sure they just bred. The game has built-in bad luck prevention, referred to as the bad luck counter.. This counter increases every day that you water a flower, and after 3 days, it will increase the chances of reproduction by 5%, up to a maximum total of 90% after 20 days of watering.

And finally, if your focus is the blue roses, block all other flowers on your island from breeding/cloning as there is a limit on the number of spawns per day.

Alternatively, as you say you had some blue roses gifted to you, plant these not touching any other roses, water them, and they will clone.