This Digital Squares tutorial is quick and simple, creating an unusual effect for banners, backgrounds and buttons.
Open a new image in PS, and press D on your keyboard.
Go to Filter > Render > Difference Clouds, Filter > Noise > Add Noise. Choose 400%, Uniform, Monochromatic and click Ok.
Go to Filter > Pixelate > Mosaic, and set the Cell Size to 13. Go to Filter > Stylise > Glowing Edges.
Change the settings to 2, 8, 3 and click Ok.
Now colourise your image (if you don’t know how, have a look at my colourising tutorial). If you don’t want a black background, go to Image > Adjustments > Invert before you colourise.
Click to enlarge the final results: