If you DON'T use a water repellent, it'll stain the wood even more.
I've had good success with Cuprinol. Got it at Sherwin Williams paint store.

Absolutely: water will do more than just stain your deck if you do not use water repellent. And it will not just stain the surface, but deep down. The water needs to go somewhere if it is not sloped to run off the side. If it does not bead on the surface, it absorbs into the wood and feeds micro-organisms that eat and add to the decay of the wood. Pressure-treating only slows it down.

Moreover, water-repellant products only bead water for so long before they lose their beading properties. But they still continue to protect the wood, just like the pressure-treatment protects it even though its water-repellent properties ahve long faded. You should not avoid water-repellent products because the water beads in the first month or so unless you are intentionally trying to age the wood or serve some other purpose.