Here is a photo I've tried to improve with little success. I generally resort to curves to fix color problems, but this one I can't seem to get right; it's as if there's not enough color information in the picture.

A bit difficult to edit, maybe it can be improved:

This time I used:
GIMP>Colors>Color Balance
G'MIC>Colors>Mixer [PCA]
G'MIC>Colors>Color Grading
G'MIC>Testing>Garagecoder>LMS Adjustment
G'MIC>Colors>Curves
G'MIC>Colors>Saturation EQ
G'MIC>Details>Equalize Local Histograms

Better than I've been able to do!

I used white balance then fill rotate to straighten out the picture. Did not have time to work with reflections red eyes or glare.

I took iarga's version and worked a little further. Forgot to keep track of my changes. Sorry.

A bit of wavelet denoise and some small healing tool work.

Last one, I promise. Hue and Saturation brought out more color in the skin. Not so washed out by the flash.

I couldn't be bothered straightening it up like others did beautifully.
Was a challenge just to get the colour right. I hope I did anyhow.

Tried it again straightening and cropping this time

I like this one. The most frustrating thing is getting the red right for the skin tones without making the kids look like they've just run a 5K. Yes, clearly the flash is a problem, and this is definitely derived from film (these people are all middle-aged now).

Edit: Removed my outcome. Didn't like it myself

Is there any known technique for dealing with this kind of image improvement?
Some methodology that defines a better approximation, sequence of steps, etc.

I think if there was a more scientific approach to the treatment of these types of images the editing would be less labor intensive (I'm not talking about restoration, which aims to remove blemishes, ripped parts of the photos, etc).

Iarga exhibited a number of used G'MICs filters, even tried it, but I had no idea how to use them, it would take more time to learn to use those filters than to finish editing this image.

Without a methodology, just exploring possibilities for now was the best I could get.


Below, original image - Post #1

Krikor, you have done a beautiful job! The coloring of the kid's faces is the best and clothing colors also. If I may ask, what did you do to get such a fantastic result? I have several old photos with a heavy red cast that I cannot do a very good job fixing. Maybe your method would work. I am willing to try most anything.

I'm not seeing these in Fx-Foundry. Help?

Just to clarify: Do you have any FX-Foundry plugins available in your setup? If you do, there should be a separate menu item at the top of the work area [File, Edit, Select, View Image ... etc.] If you don't see the menu item, you may not have any FX-Foundry scripts at all.

They are still available on the web, but the FX-Foundry scripts collection was put together for earlier versions of GIMP. Many of those scripts will not work "out of the box" in contemporary versions. Many have been rewritten (some for python instead of scheme) under other names and are no longer under an FX-Foundry listing.

Paul Sherman maintains a number of updated versions of many older GIMP SCM scripts at gimphelp.org.