In DragonVale for the iPad, iPhone, and iPod Touch, the Blue Moon Dragon is a limited dragon that is only available during months that have a blue moon, which by today’s standards is to have two full moons in one month.
By these standards, this event will only happen every two to three years. The previous event only lasted a couple days as well, so this will certainly be one of the more limited dragons out there.
To breed the Blue Moon Dragon, you need to mix a lightning type dragon with a cold type dragon.
Check out my DragonVale Breeding Guide for more dragon breeding combinations.