I’ve been scanning and organizing old photos.

The photo on the left was from a balloon festival in Columbia, South Carolina in 1985.  It’s not a scanning problem, the photo looks like that.  I don’t know if it always did, or got that reddish tint with age. 

Film photography relies on chemical processes.  The photographer could add filters to get an effect like this, but the developing process also influenced the final photo.  Serious photographers developed their own film to get the desired result.  Over time, those chemicals may degrade.

Without knowing much about GIMP software, selecting the “White Balance” significantly improved the photo.  Some color was lost on the more distant balloon, but overall, I prefer the photo on the right.