Adobe Photoshop: Lightning effect 6
First you need to use the gradient tool and shade black to grey.

Go to Filter>Render>Difference Clouds and keep doing Difference Clouds until you get the BLACK to look how you want to. In this case it only took one time. Note: It may take more than one attempt to get the Difference Clouds to look good.

Now go Image>Adjust>Invert. You should get a light colored picture. Now we can fix that.

Now go to Image >Adjust>Levels. Move the middle arrow all the way to the right. Then move the arrow on the left to get the desired amount of clouds.

Now go Image>Adjust>Hue/Saturation. Click colorize and get the desired color. You don't have to add color if you don't want to.

Now erase all the clouds around the edge of the picture that you don't want to keep.
Now you can go Image>Rotate Canvas to get the lightning to face the desired directon