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You can dye leather pretty easily and I would recommend doing this outdoors, if possible. You basically clean the surfaces, then dampen them with water, apply the dye and allow to dry, and then buff and apply a leather finish.
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Best of Luck, Brian
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I would get a leather dye which you could find at your local fabric/ craft store. A fabric store will be more likely to have samples of dyed leather. You can also buy it online, but it is hard to judge the final color that you will get; with black you may be alright though.
You may have to look under leather stains:
Here are a couple that I found: