Ken, I can't think of any grease or oil that won't darken leather. I don't much care for the cleaning and oiling properties of Lexol, most leather manufactures that make a recomendation, recomend lexol, but it seems that it would be the best bet if you really want to go this route. It would be best if you tried a small area that can't be seen before you start.
My thoughts would be to wear it!! As often and as long as you can. It won't take long till it starts to display your personality!!
Good luck on this quest!
Butler Ford