If u think logical, a rainbow dragon is a dragon of all the elements. Means earth, plant, fire, cold, lightning, water and air.
I hear that if u breed crystal- and a blazing dragon u will get a rainbow dragon, wich makes logical sense.
•Crystal is a mix of lightning and earth
•Blazing is a mix of air and fire
Now we have four of seven elements, three left - plant, cold and water.
And if we go back to the Blazing dragon u will, as mentioned, need air and fire, wich also make sense. Instead of using the normal fire dragon use either flower- or blue fire dragon.
•Flower is a mix of fire and plant
•Blue fire is a mix of fire and cold
Now... The only thing missing is the Air dragon, wich needs a fire- and a water dragon. Instead of using normal fire dragon use either Flower- or a Blue fire dragon. Depends on what dragon u choose when u breeded the Blazing dragon.
So if u look at all, u have now included all the elements u needed.
BUT all of this is just a hypotethical. For me this makes all sense for breeding a Rainbow dragon. I haven't come so far that i've got the Rainbow dragon, only to the air dragon, wich i now are waiting for to hatched. As for ur information i used a Flower- and a water dragon.
Just wanted to share this information to all of u