Width: 200 pixels
Height: 600 pixels
Resolution: 72 pixels/inch
Color Mode: RGB Color | 8 bit
Background Contents: White
Draw a gradient, that looks something like the picture below, using the Gradient Tool with your color foreground colors set to black and white . To get this effect simply click in the center of the document on the left side and while holding down the left mouse button drag a line across to the right side as shown below on the left. The picture on the right is how is should look after you unclick your left mouse button:
The next step is to apply the filter Different Clouds by clicking Filter > Render > Differentiate Clouds. Once you have applied the filter it should look like the picture on your right:
The next step is to Invert the image by hitting the shortcut Ctrl + I on your keyboard.
Adjust the picture’s levels by creating a level's adjustment layer. Click on the adjustment layer button on the layers palette and select levels from the drop down option:
Drag the middle slider all the way to the right.
The final step is to color the lightning, this can be done by adjusting the picture’s Hue/Saturation (Enhance > Adjust Color > Hue/Saturation):
Make sure colorize is checked. These are the settings I used:
Here is my finished product: