Or bring them to a high quality, professional printers. Have them scan the print into a high quality, high megapixel jpeg. Then fix the jpeg with photoshop using the tint controls or white balance. Make a new print.
There are even some places online that you can send the jpeg to to have a new 20" x 15" poster size photo made. Or that same printer you took the print to.
Just be aware though, some printers will not make copies of work that is not original, due to copyright laws. Then you'd have to go the route of taking a picture of the print, as stated above.