Here are some paraphrased usage examples for Double Rainbow, (DR can be used in place of Double Rainbow), from NathanFillion on his Twitter page, among others:

"That pizza was so Double Rainbow (DR). Oh my god."

"Possible responses to "Double Rainbow": -Double Rainbow, all the way. -Starting to look like a TRIPLE Rainbow. -What does it mean?" Answer: "A Full-on Double Rainbow!"

The movie Serenity is so vivid, it's Double Rainbow all the way!

Having a second season of Firefly? Definitely Double Rainbow!.

The brilliance of Nathan Fillion is so intense, it's Double Rainbow all the way! (DR ATW!)