Here's how I fake it.

Decide on a node to drive the contours of the iridescence - it can be a diffuse, a specular, a phong, a clouds, or a combination of those.

Plug that into a math node with a multiplier of 6 to 10. Set the math function to Mod and Value_2 to 1.

Take that node and plug into a color ramp. Set the colors roughly to RED, YELLOW-GREEN, CYAN-BLUE, MAGENTA.

The color ramp is your iridescence - use it however you'd like. I'll give a few examples, but you usually want to lightly mix it with something else. There is a lot of tweaking involved too. I'll leave that to you!

First some simple bubbles, not using refraction here, just simple transparency. However, they need reflection on the edges to look right.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)