Demo

Direction

1. File > New > any size (mine used 200x200 px) with black background.

2. Press D.

3. Filter > Render > Clouds.

4. Filter > Brush Strokes > Accented edges, use default settings.

5. Now go to Filter > Pixelate > Mosaic... with Cell size 10 px.

6. Go to Filter > Sharpen > Sharpen.

7. Ctrl + F 4 times.

8. Press Ctrl + U > check Colorize > play around with the colors or use my settings.

9. You are done. :-)