1. New image, 300 x 300 pixels and any background.
2. Filter > Render > Clouds.
3. Filter > Liquify, and smear those clouds all over the place.
4. Press Ctrl + L to bring up the levels dialogue, and select Auto.
5. Press Ctrl + U, check colourize, and use Hue: 83, Saturation: 40 and ...
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