Okay, so this is something abit different, I haven't made a tutorial like this. It is going to be very simple. With Gimp 2.6.7 but you can do this with any gimp program. This is just a guideline so you might need to change somethings for your image. If there are any questions left feel free to ask away!
Going from:
to
Okay so to start with we are going to duplicate the base picture and open colour balance.
red 80
green 80
and leave everything else.
then set that layer to grain merge at 100%
You should have this so far:
Now we need to make a new layer fill it with #001234 and set it to screen at 60%
Make anothe new layer and fill it with #ff7c4c and set it to multiply at 40%
Make another new layer fill it with #001234 and set it to screen ar 50%
You can stop here if you like how it looks or you can..
Duplicate the base image and bring it to the top, then desaturate it.
then open levels:
Input
0 - 1.00 - 255
Output
75 - 255
and then set that to overlay at 50%
and im finished with this:
Picture credit to : Evie.