IF... The problem is efflorescence then these pointers might help future Houzz'ers with the same problem: What is Efflorescence and How Can I Clean It? https://www.paverwash.com/efflorescence-can-clean/ If it is bleach damage, and since the pavers can't be purchased, might try chiseling out the grout and turn over the damaged pavers, after cleaning them. Just a thought.

Paint on concrete doesn't look good or hold up well. You might check into concrete stains if you want to change the color. I haven't seen the stain used on pavers, but it might be possible. There is a masonry adhesive that comes in a tube that we used to anchor flagstones to a concrete-block support structure -- similar to what you have. It was not available at HD, but our local stone supplier had it. It is applied with a caulking gun, is extremely strong, and will hold up to freezing. The stone yard told us the stone would give up before the adhesive would. Definitely go with the polymeric sand. We've been very happy with how it hold up and keeps weeds out.

I think the mix of sandstone and wall is fine. Not sure how I feel about a brown border as that brown feels more red. I would think a tan border would pull it together.

Consider that before paver companies got so creative, it began with a simple brick shape and only a couple of colors. The colors are usually not pure, but mottled as part of the manufacturing process. (Cannot tell from the mfg. literature if this is the case here.) There are innumerable attractive, time-tested patterns that can be constructed with the standard brick shape: basketweave, herringbone, running bond, modified basketweave, stacked bond & probably more. I doubt that anyone who installed paving from these simple options was unhappy with the result. Personally, I prefer these 'old school' options. They always looks nice and stand the test of time, while many of the new color ranges and patterns that have been developed since, look unpleasant from the day they are installed! The one's with sharply contrasting colors in the mix look blotchy and garish to me. The one's with high texture can be difficult to walk on, if ever someone would show up in heels for the patio party. Barefooters might not care for them either. The 'Miami' model, with its uniformly wavy edge and perfectly rounded corners, looks like a fakey facsimile to me. I don't care much for the one they call 'Cobblestone.' 'Old Canada' seems OK in the picture, if the color is not too wild. But you cannot go wrong with the 4" x 8" brick. Another one I've found to look very good is the 4" x 4" square in running bond configuration. An important fact to keep in mind with paving is that light colors reflect the sun and can be absolutely blinding. It's almost always the case that darker is better. I would stick with grey, charcoal or red. I would also forget about white cement. It's for those who love a purer color, but generally, this is not an improvement outdoors. Usually, white cement costs more, too. Whatever you do, you can only get so far in narrowing choices via online or print materials. When you get it honed down to two or three possibilities, you must go to the paver yard and get samples. It is the only way to know if you're going to be satisfied with the end result. Get a half dozen of each sample so that you can mock up enough to give an idea of the result. Look at it on site from a distance in order to get the best feel for how it will look with its surroundings.