Repairing old Ektachrome slides

[hornetster]

Have hundreds of old slides to scan in, and unfortunately, the majority of them seem to be Kodak Ektachrome, and have a red/brown tinge to them.
Is there a good tutorial around, or an "easy fix" to correct this? (He says, hopefully...)
Sample:     

[rich2005]

This is how I might apply a correction.

White balance the image, Depends on the image. Colors -> Auto -> White Balance might give a satisfactory result or manually , Colors -> Levels  and pick white and black points from the image.

Duplicate that and set the layer mode to Screen.  Now colorize that layer, I use the GEGL filter Tools -> GEGL Operation -> Color Overlay Pick Green and adjust (to very dark green). Keep an eye on the subjects in the image.  This is just a variation on a well-known procedure for underwater photos.

If more is needed, then Layer -> New from Visible and work on that

Depends on the image, if the background is a bit bright, Using Ofnuts luminosity plugin from http://sourceforge.net/projects/gimp-too...s/scripts/  ofn-luminosity-masks.zip dated 2019-12-01
It makes a selection. Background adjusted for brightness, selection inverted and contrast adjusted, 

   

Duration 2 and a half minutes https://youtu.be/YGltUgHejco

[Ofnuts]

Otherwise, the Green channel is mostly gone,  so another options is to convert to B&W using Colors ➤ Desaturate ➤ Mono mixer, set the Green to 0, and use a bit of the red (0.2) and a lot of blue (.9) (adding blue adds contrast), and then increase contrast:

   

[hornetster]

Thanks for the tips!
Will have a play.