I made the original version of this icon in green. The background is just this horizontal gradient that goes from white to green to black.
The rest of the effect is just a bunch of rings, so I made a big one.
From there, I copy-pasted and resized it a bunch of times to get a nice cloud of rings.
After that, I just copied and rotated it, threw on a blur effect, and I was done. Easy icon.
The rest are just re-colors.