First, you need to find out the genus of the animal from which the leather was taken (hopefully with the animal's blessing or, if it was too late for that, then that of the head slauterhouse chop-dude). This is important to understand the grain and texture of the leather - texture and, therefore, dye absorption varies greatly between animal families, although it's widelyy known that "Old Goats" are pretty set in their ways (and hues) and it may be difficult to alter the color(s) of old goat leather.
Next, you need to find out exactly which brand and year of distilation the whiskey was that they fed to the animal before he was, er..., "volunteered" to provide the hide. That way, you'll get a much better color match.
Probably the best bet would be to drink a sizeable amount of the aforementioned whiskey which will, hopefully, get you to forget that you have a mismatch in the first place.
Lastly, and this is important, if the leather that you have has some areas shaded darker or lighter than other areas of the same hide, then it's gonna be really, really hard to darken or lighten just one area and have it match the surrounding without looking like it has been, um...., adjusted.