It means that which is:
"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!)
"Oh, yeah. Cool. Enjoy it, loca"