What I Tried
I have been drawing shapes with pen tool then filling with the gradient mesh tool in Illustrator. To try to feather the edges of the mesh I make each of the outside anchor points set to 0% opacity however I’m stuck on how to manipulate the object to look like a ripple as shown in the pictures below.
The colours seem to flow according to the structure of the ripple, is this done by manually eyedropping the anchor points or is there a specific technique to achieve this effect that I’m missing? It might be done via Photoshop but I’m not sure, suggestions for Photoshop or Illustrator would be appreciated.
In Photoshop, chose the Gradient tool, set the mode to Difference, and swipe swipe swipe. Use gradients with various colors for more effect. Here’s 4 swipes with a radial gradient, from bottom left.
(eta) You can also use the Smudge tool afterwards.