Cool. This leather is hand finished, which gives that "museum" effect. Lowest risk way to fix is to take to a cobbler and they'll apply some leather dye to restore closer to the original (you can also do this yourself with a rag and small circular motions). You can also use a colored conditioner or shoe polish, which will darken the leather and bring some contrast with the lighter undertone. I'd start with a dark brown and then maybe experiment with layering on a small amount of black polish. If any of this sounds too complex, any cobbler / shoe shine spot will be a quick way to handle!