Hi all...Need a professional opinion....I recently had sagging slab removed from existing raised concrete patio built on cinderblock. (See attached photos)..It was replaced w/a colored/stamped concrete slab. The top course of cinderblocks was replaced but the lower old ones were left in place to save $$. The old top used to sag toward house and rain would puddle outside of doorwall so we would sweep it off onto the driveway and it would stay against the block until it dried for awhile. (That part of the driveway has also been replaced to drain away). Problem now is we would like to stain the cinderblock to match the stamped top but the side where we used to sweep the water off has some blackened blocks (see photo)..There are a few other areas where the blocks are darker also. We had talked to the contractor who did the new work about staining the cinderblock to match the new slab and he recommended we go to Sherwin Williams. I asked the Sherwin Williams guy what the best type would be and if we should use a type that seals the block, or one that allows it to still breathe since water can still come up though the ground and will try to escape through the block...(I'm thinking that sealing it may hold all moisture and water in and that might not be a good thing)....He just said "thats a good question... I don't know the answer to that one". ?? I can't seem to find anything about it online either. He recommended starting out scrubbing it with Dawn dish detergent and powerwasing to get the black off no matter what we used after. I did that but it hardly removed anything. I also tied a 50/50 mixture of bleach/water on the black parts but that did nothing either. Im afraid to use anything more powerful because it will be rinsing down onto new ground level slab and I don't want to risk it ruining the sealer on that. Im now to the point in thinking that, if I can't get the black off, I'm going to have to go with a very dark brown instead of a matching color just to hide it. I'm hoping to get a professional opinion on: A. Do we need to use a special type of stain so that concrete can still breathe and release moisture or is it ok to seal it? B. Is there something I can use to remove the black without worrying about it ruining the sealer on the lower part as it runs down or when I rinse it off? (While I'm at it....I will be building a Pergola over the top soon too. Any advice on the best brackets to use the keep moisture from wicking up into the post? Home Depots weren't raised to prevent this)? Thanks !