If your porch is concrete, I recommend UGL from Home Depot. That's what Mary and I used years ago when she got the hare-brained idea to paint her garage floor. Turns out it wasn't a hare-brained idea--it looked so much better, and lasted a long time.
At that time, it only came in gray. We chose the lightest gray and it really lit up the garage...and it does look darker once it is on. We put on two coats and it was easy, easy, easy to apply with rollers.