How to breed a rainbow dragon

I GOT A RAINBOW DRAGON ON DRAGONVALE!!!!
Seriously this works you have to try it a few times but I got it on my second go

Breed: Evergreen+Forge

If it takes less than 40hours then it's a forge or something like that. If it takes over 40 hours its either a gold, silver or rainbow

WARNING
It worked with me when I was listening to gangnam style

WARNING 2
You need a breeding cave!