Going from
this to
in what is possibly the simplest tutorial ever.
1) Crop the picture, sharpen it.
2) Duplicate the base three times. Set the first two to screen. Set the last to overlay at 50.
3) On the main GIMP interface, go to your chosen foreground color. Change it to 091442
4) Create a new layer selecting foreground color on layer type fill. Duplicate that layer four times so you have five copies of your blue layer.
5) Starting with the first (closest to the base) blue layer, set them to screen 100, subtract 100, screen 100, subtract 50, and screen 100.
6) Create a new white layer (ffffff) and set it to overlay at 40. Flatten the image.
7) Optional - you can duplicate your base layer, bring it to the top and set it to overlay at 30. It gives it a sharper image.
8) Optional - I added "Cristina" at the bottom after I flattened the image. I used the very nice text "Ambulance".
And that's it! I'd love to see your results! :-)