Never heard of a stain blocking paint. There are paints that claim to be a primer and topcoat with two coats, but nothing that I would trust to block stains.

There are solid color oil and latex stains that look like paint to most people and they are effective for cedar and other tannin heavy woods.

sorry for not clarifying-I'm looking for a Kilz type product that may be tinted to closely match an interior color used in a high volume apartment complex...used to block water stains on the ceiling

Most oil base primers can be tinted with 2 oz. universal colorant, Kilz included. That limits you to only fairly light colors and it takes a fairly skilled tint man to get you super close. Usually "in the ballpark" will be just fine. As for a topcoat, only true stain blocker would be oil and that is something you probably would not use on your jobs. My advice would be use the oil primer tinted as close as you can get it for the first coat and then just apply the proper latex topcoat over that when dry. Simple really. Don't know of any deep tinting base oil primers though if you ever need it.

IF it HAS to be one coat, I suppose if it is not high end work and just appt. repaints, you could just use the tinted oil as the only coat. Not the proper way to do it, but if it's gotta be done... It would of course be a FLAT sheen.