Very nice porch upgrade! I particularly like your choice to have the Bluestone rock-faced. It makes the job look so much better than a simple sawn or flamed edge.

For sealing without any change in appearance, you could check out the Stone Tech proffesional product line. I don't really think any sealer will truly prevent oak leaf discoloration completely. In my experience the brown stains from fall's leaves will fade away on it's own after the leaves are gone & a bunch of rain has rinsed the stone.

Here is a link that might be useful: Stone Tech Sealer

Thank you for your comments and information. The rock face was my idea after seeing it at a local fine furniture store in Old Saybrook, CT. The job on this building was unbelievable and no expense was spared with workmanship (stone and wood). I quickly went to the same stone yard they used and changed my order to rock face. Makes a huge difference. ;-)