Many products will darken leather if the leather is not a finished leather. If you ride a lot in hot sunny conditions, or get caught in the rain, you will need to condition it several times during the season. You can usually tell when your jacket or chaps feel dry. Incidentally, rain will really dry out leathers because when the rain evaporates from the jacket, it pulls moisture away from the skin. I would recommend conditioning your jacket once it dries if you are unfortunate enough to get caught without your raingear.
Many people swear by mink oil to condition and waterproof their jacket.
The way I describe it to customers is mink oil vs Lexol is like putting Vaseline on your hands vs Jergens lotion. Mink oil will clog the pores of your leather just as Vaseline creates a barrier between your skin and the environment. That's why it will make your jacket waterproof. It will also eventually dry out your leather because the pores are clogged. You will also notice your jacket may have a whitish haze to it.