I think Fradctal Noise would be your best bet. Have fun with the color-changing plugins and trackmattes for other looks.
There's no one simple plugin to generate the look you've provided, but a combination of gradient generators, fractal noice and some distortion tools should do the trick.
Also remember that you can create mutli-coloured gradients using Layer Styles.
There are also some third party gradient options, such as:
YY Ramp +
RevisionFX' RE:Fill has a "blend" mode that mends hols by interpolating with gradients. This can be used with masks that have colored stroke effects applied to create something similar to gradient meshes. Generally, though, it's not a typical workflow. Most such effects would be done using other methods for a number of reasons. Since you have not provided any details on what you are actualyl trying to achieve, nobody can say much, though.