If you use SnoSeal, no color leaching will occur. Just heat the saddle in the oven on low. Then, with some type of applicator, like a foam paint brush, slather it on the underside only. It'll melt in like butter on toast. A very light coating on top with your fingers, otherwsie it could get a bit sticky in hot weather. Buff off the top after the saddle has cooled. The SnoSeal will not over condition leather and will add good water resistance.

If you use Proofide, as MnHPVA says, you won't need to re-apply it for at least six months.