Fire
A Current Dragon or a Hail Dragon. It depends what shade of blue it is. Dark blue is Current Dragon and light blue is Hail Dragon.
The most effective method of breeding a hail dragon is using a cold dragon and lightning dragon. This has a 28% success rate. The egg is light blue with a light green bolt, and takes 8 hours to hatch.Some other (slightly less effective) methods are:blue moon + blue moonsonic + stormstorm + fireflyice + lightning
The hail dragon starts as a light blue egg with a teal bolt. After hatching, it is a purple dragon with a cube of ice on the end of it's tail. As it ages, it develops yellow wings. There are icy blue spikes coming from its face.
It varies
You can't maybe you can if you have jailbreak I think........
A storm dragon egg in Dragonvale is formed when a storm dragon mates with a moon dragon or a sun dragon. The egg looks yellow in color with a blue outline. It also has white snowflakes.
This will be a crystal dragon.
Lava dragon
Crystal dragon
about two hours
The most effective method of breeding a victory dragon is using a snow dragon and lightning dragon. This has a 21% success rate. The egg is gold with gold wings, and takes 36 hours to hatch.
A rainbow dragon looks magnificent, especially by a sun dragon. It breathes rainbow stars and gives a lot of money. Mix something that has 48 hours and expect it to be either sun, moon, or a rainbow dragon.