I haven't used it on leather intentionally, but I do know it stains. Experimentation is probably in order, the grape must (the solids left over from wine making) will possibly make for a good base, though it has a strong odor. Take those solids and make a strong tea from it.
If I were to use wine, I would probably want to reduce it down to remove the alcohol and some water, might darken it up as well.
As someone else mentioned above, a wood stain may be the most consistent way to get the color you want. Most hardware stores carry it.