Ok, I'm MeMB and i use the GIMP, which can be downloaded
freely from www.gimp.org
The tutorial:
Alright, im gonna teach you how to get effects like this:

So, lets get started then. I presume you have the latest version (GIMP 2.2).
Ok, first open up a new document, i used 800x800
Then color the background black.
Now set the foreground color to pure white and the background color also to pure white.
Then select Filters --> Render --> Nature --> Flame
A window will pop-up. Click on the edit button next to the example picture.
Choose Random as style and click Randomize a few times until you get the desired effect.
Then leave the Edit window. Drag Sample Density all the way to the right. (This increases the detail).
Now go to the camera tab. Drag around the X and Y sliders and use Zoom to make it cover a little over half of the image. Also position it to the right. Use the Example pic as a reference. When you're happy with the setings, click ok.
Now go to Layer --> Colors --> Color Balance
Adjust the sliders so that the flame turns out red. Also use the radio buttons to change the different tones independently
Now if the flame looks a bit dull use Layer --> Colors --> Brightness and Contrast to liven up the pic by adjusting the sliders
Now create a new layer, and call this Flame2.
Repeat all previous steps except for making a new layet. Also color this flame blue instead of red.
That should do it!
My result:

Have fun!
~MeMB